]> git.vpit.fr Git - perl/modules/re-engine-Hooks.git/blobdiff - src/5020002/orig/regcomp.c
Add support for perl 5.20.2
[perl/modules/re-engine-Hooks.git] / src / 5020002 / orig / regcomp.c
diff --git a/src/5020002/orig/regcomp.c b/src/5020002/orig/regcomp.c
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+/*    regcomp.c
+ */
+
+/*
+ * 'A fair jaw-cracker dwarf-language must be.'            --Samwise Gamgee
+ *
+ *     [p.285 of _The Lord of the Rings_, II/iii: "The Ring Goes South"]
+ */
+
+/* This file contains functions for compiling a regular expression.  See
+ * also regexec.c which funnily enough, contains functions for executing
+ * a regular expression.
+ *
+ * This file is also copied at build time to ext/re/re_comp.c, where
+ * it's built with -DPERL_EXT_RE_BUILD -DPERL_EXT_RE_DEBUG -DPERL_EXT.
+ * This causes the main functions to be compiled under new names and with
+ * debugging support added, which makes "use re 'debug'" work.
+ */
+
+/* NOTE: this is derived from Henry Spencer's regexp code, and should not
+ * confused with the original package (see point 3 below).  Thanks, Henry!
+ */
+
+/* Additional note: this code is very heavily munged from Henry's version
+ * in places.  In some spots I've traded clarity for efficiency, so don't
+ * blame Henry for some of the lack of readability.
+ */
+
+/* The names of the functions have been changed from regcomp and
+ * regexec to pregcomp and pregexec in order to avoid conflicts
+ * with the POSIX routines of the same names.
+*/
+
+#ifdef PERL_EXT_RE_BUILD
+#include "re_top.h"
+#endif
+
+/*
+ * pregcomp and pregexec -- regsub and regerror are not used in perl
+ *
+ *     Copyright (c) 1986 by University of Toronto.
+ *     Written by Henry Spencer.  Not derived from licensed software.
+ *
+ *     Permission is granted to anyone to use this software for any
+ *     purpose on any computer system, and to redistribute it freely,
+ *     subject to the following restrictions:
+ *
+ *     1. The author is not responsible for the consequences of use of
+ *             this software, no matter how awful, even if they arise
+ *             from defects in it.
+ *
+ *     2. The origin of this software must not be misrepresented, either
+ *             by explicit claim or by omission.
+ *
+ *     3. Altered versions must be plainly marked as such, and must not
+ *             be misrepresented as being the original software.
+ *
+ *
+ ****    Alterations to Henry's code are...
+ ****
+ ****    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
+ ****    2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
+ ****    by Larry Wall and others
+ ****
+ ****    You may distribute under the terms of either the GNU General Public
+ ****    License or the Artistic License, as specified in the README file.
+
+ *
+ * Beware that some of this code is subtly aware of the way operator
+ * precedence is structured in regular expressions.  Serious changes in
+ * regular-expression syntax might require a total rethink.
+ */
+#include "EXTERN.h"
+#define PERL_IN_REGCOMP_C
+#include "perl.h"
+
+#ifndef PERL_IN_XSUB_RE
+#  include "INTERN.h"
+#endif
+
+#define REG_COMP_C
+#ifdef PERL_IN_XSUB_RE
+#  include "re_comp.h"
+EXTERN_C const struct regexp_engine my_reg_engine;
+#else
+#  include "regcomp.h"
+#endif
+
+#include "dquote_static.c"
+#include "charclass_invlists.h"
+#include "inline_invlist.c"
+#include "unicode_constants.h"
+
+#define HAS_NONLATIN1_FOLD_CLOSURE(i) \
+ _HAS_NONLATIN1_FOLD_CLOSURE_ONLY_FOR_USE_BY_REGCOMP_DOT_C_AND_REGEXEC_DOT_C(i)
+#define IS_NON_FINAL_FOLD(c) _IS_NON_FINAL_FOLD_ONLY_FOR_USE_BY_REGCOMP_DOT_C(c)
+#define IS_IN_SOME_FOLD_L1(c) _IS_IN_SOME_FOLD_ONLY_FOR_USE_BY_REGCOMP_DOT_C(c)
+
+#ifndef STATIC
+#define        STATIC  static
+#endif
+
+
+struct RExC_state_t {
+    U32                flags;                  /* RXf_* are we folding, multilining? */
+    U32                pm_flags;               /* PMf_* stuff from the calling PMOP */
+    char       *precomp;               /* uncompiled string. */
+    REGEXP     *rx_sv;                 /* The SV that is the regexp. */
+    regexp     *rx;                    /* perl core regexp structure */
+    regexp_internal    *rxi;           /* internal data for regexp object
+                                           pprivate field */
+    char       *start;                 /* Start of input for compile */
+    char       *end;                   /* End of input for compile */
+    char       *parse;                 /* Input-scan pointer. */
+    SSize_t    whilem_seen;            /* number of WHILEM in this expr */
+    regnode    *emit_start;            /* Start of emitted-code area */
+    regnode    *emit_bound;            /* First regnode outside of the
+                                           allocated space */
+    regnode    *emit;                  /* Code-emit pointer; if = &emit_dummy,
+                                           implies compiling, so don't emit */
+    regnode_ssc        emit_dummy;             /* placeholder for emit to point to;
+                                           large enough for the largest
+                                           non-EXACTish node, so can use it as
+                                           scratch in pass1 */
+    I32                naughty;                /* How bad is this pattern? */
+    I32                sawback;                /* Did we see \1, ...? */
+    U32                seen;
+    SSize_t    size;                   /* Code size. */
+    I32                npar;            /* Capture buffer count, (OPEN) plus
+                                           one. ("par" 0 is the whole
+                                           pattern)*/
+    I32                nestroot;               /* root parens we are in - used by
+                                           accept */
+    I32                extralen;
+    I32                seen_zerolen;
+    regnode    **open_parens;          /* pointers to open parens */
+    regnode    **close_parens;         /* pointers to close parens */
+    regnode    *opend;                 /* END node in program */
+    I32                utf8;           /* whether the pattern is utf8 or not */
+    I32                orig_utf8;      /* whether the pattern was originally in utf8 */
+                               /* XXX use this for future optimisation of case
+                                * where pattern must be upgraded to utf8. */
+    I32                uni_semantics;  /* If a d charset modifier should use unicode
+                                  rules, even if the pattern is not in
+                                  utf8 */
+    HV         *paren_names;           /* Paren names */
+
+    regnode    **recurse;              /* Recurse regops */
+    I32                recurse_count;          /* Number of recurse regops */
+    U8          *study_chunk_recursed;  /* bitmap of which parens we have moved
+                                           through */
+    U32         study_chunk_recursed_bytes;  /* bytes in bitmap */
+    I32                in_lookbehind;
+    I32                contains_locale;
+    I32                contains_i;
+    I32                override_recoding;
+    I32                in_multi_char_class;
+    struct reg_code_block *code_blocks;        /* positions of literal (?{})
+                                           within pattern */
+    int                num_code_blocks;        /* size of code_blocks[] */
+    int                code_index;             /* next code_blocks[] slot */
+    SSize_t     maxlen;                        /* mininum possible number of chars in string to match */
+#ifdef ADD_TO_REGEXEC
+    char       *starttry;              /* -Dr: where regtry was called. */
+#define RExC_starttry  (pRExC_state->starttry)
+#endif
+    SV         *runtime_code_qr;       /* qr with the runtime code blocks */
+#ifdef DEBUGGING
+    const char  *lastparse;
+    I32         lastnum;
+    AV          *paren_name_list;       /* idx -> name */
+#define RExC_lastparse (pRExC_state->lastparse)
+#define RExC_lastnum   (pRExC_state->lastnum)
+#define RExC_paren_name_list    (pRExC_state->paren_name_list)
+#endif
+};
+
+#define RExC_flags     (pRExC_state->flags)
+#define RExC_pm_flags  (pRExC_state->pm_flags)
+#define RExC_precomp   (pRExC_state->precomp)
+#define RExC_rx_sv     (pRExC_state->rx_sv)
+#define RExC_rx                (pRExC_state->rx)
+#define RExC_rxi       (pRExC_state->rxi)
+#define RExC_start     (pRExC_state->start)
+#define RExC_end       (pRExC_state->end)
+#define RExC_parse     (pRExC_state->parse)
+#define RExC_whilem_seen       (pRExC_state->whilem_seen)
+#ifdef RE_TRACK_PATTERN_OFFSETS
+#define RExC_offsets   (pRExC_state->rxi->u.offsets) /* I am not like the
+                                                         others */
+#endif
+#define RExC_emit      (pRExC_state->emit)
+#define RExC_emit_dummy        (pRExC_state->emit_dummy)
+#define RExC_emit_start        (pRExC_state->emit_start)
+#define RExC_emit_bound        (pRExC_state->emit_bound)
+#define RExC_naughty   (pRExC_state->naughty)
+#define RExC_sawback   (pRExC_state->sawback)
+#define RExC_seen      (pRExC_state->seen)
+#define RExC_size      (pRExC_state->size)
+#define RExC_maxlen        (pRExC_state->maxlen)
+#define RExC_npar      (pRExC_state->npar)
+#define RExC_nestroot   (pRExC_state->nestroot)
+#define RExC_extralen  (pRExC_state->extralen)
+#define RExC_seen_zerolen      (pRExC_state->seen_zerolen)
+#define RExC_utf8      (pRExC_state->utf8)
+#define RExC_uni_semantics     (pRExC_state->uni_semantics)
+#define RExC_orig_utf8 (pRExC_state->orig_utf8)
+#define RExC_open_parens       (pRExC_state->open_parens)
+#define RExC_close_parens      (pRExC_state->close_parens)
+#define RExC_opend     (pRExC_state->opend)
+#define RExC_paren_names       (pRExC_state->paren_names)
+#define RExC_recurse   (pRExC_state->recurse)
+#define RExC_recurse_count     (pRExC_state->recurse_count)
+#define RExC_study_chunk_recursed        (pRExC_state->study_chunk_recursed)
+#define RExC_study_chunk_recursed_bytes  \
+                                   (pRExC_state->study_chunk_recursed_bytes)
+#define RExC_in_lookbehind     (pRExC_state->in_lookbehind)
+#define RExC_contains_locale   (pRExC_state->contains_locale)
+#define RExC_contains_i (pRExC_state->contains_i)
+#define RExC_override_recoding (pRExC_state->override_recoding)
+#define RExC_in_multi_char_class (pRExC_state->in_multi_char_class)
+
+
+#define        ISMULT1(c)      ((c) == '*' || (c) == '+' || (c) == '?')
+#define        ISMULT2(s)      ((*s) == '*' || (*s) == '+' || (*s) == '?' || \
+       ((*s) == '{' && regcurly(s, FALSE)))
+
+/*
+ * Flags to be passed up and down.
+ */
+#define        WORST           0       /* Worst case. */
+#define        HASWIDTH        0x01    /* Known to match non-null strings. */
+
+/* Simple enough to be STAR/PLUS operand; in an EXACTish node must be a single
+ * character.  (There needs to be a case: in the switch statement in regexec.c
+ * for any node marked SIMPLE.)  Note that this is not the same thing as
+ * REGNODE_SIMPLE */
+#define        SIMPLE          0x02
+#define        SPSTART         0x04    /* Starts with * or + */
+#define POSTPONED      0x08    /* (?1),(?&name), (??{...}) or similar */
+#define TRYAGAIN       0x10    /* Weeded out a declaration. */
+#define RESTART_UTF8    0x20    /* Restart, need to calcuate sizes as UTF-8 */
+
+#define REG_NODE_NUM(x) ((x) ? (int)((x)-RExC_emit_start) : -1)
+
+/* whether trie related optimizations are enabled */
+#if PERL_ENABLE_EXTENDED_TRIE_OPTIMISATION
+#define TRIE_STUDY_OPT
+#define FULL_TRIE_STUDY
+#define TRIE_STCLASS
+#endif
+
+
+
+#define PBYTE(u8str,paren) ((U8*)(u8str))[(paren) >> 3]
+#define PBITVAL(paren) (1 << ((paren) & 7))
+#define PAREN_TEST(u8str,paren) ( PBYTE(u8str,paren) & PBITVAL(paren))
+#define PAREN_SET(u8str,paren) PBYTE(u8str,paren) |= PBITVAL(paren)
+#define PAREN_UNSET(u8str,paren) PBYTE(u8str,paren) &= (~PBITVAL(paren))
+
+#define REQUIRE_UTF8   STMT_START {                                       \
+                                     if (!UTF) {                           \
+                                         *flagp = RESTART_UTF8;            \
+                                         return NULL;                      \
+                                     }                                     \
+                        } STMT_END
+
+/* This converts the named class defined in regcomp.h to its equivalent class
+ * number defined in handy.h. */
+#define namedclass_to_classnum(class)  ((int) ((class) / 2))
+#define classnum_to_namedclass(classnum)  ((classnum) * 2)
+
+#define _invlist_union_complement_2nd(a, b, output) \
+                        _invlist_union_maybe_complement_2nd(a, b, TRUE, output)
+#define _invlist_intersection_complement_2nd(a, b, output) \
+                 _invlist_intersection_maybe_complement_2nd(a, b, TRUE, output)
+
+/* About scan_data_t.
+
+  During optimisation we recurse through the regexp program performing
+  various inplace (keyhole style) optimisations. In addition study_chunk
+  and scan_commit populate this data structure with information about
+  what strings MUST appear in the pattern. We look for the longest
+  string that must appear at a fixed location, and we look for the
+  longest string that may appear at a floating location. So for instance
+  in the pattern:
+
+    /FOO[xX]A.*B[xX]BAR/
+
+  Both 'FOO' and 'A' are fixed strings. Both 'B' and 'BAR' are floating
+  strings (because they follow a .* construct). study_chunk will identify
+  both FOO and BAR as being the longest fixed and floating strings respectively.
+
+  The strings can be composites, for instance
+
+     /(f)(o)(o)/
+
+  will result in a composite fixed substring 'foo'.
+
+  For each string some basic information is maintained:
+
+  - offset or min_offset
+    This is the position the string must appear at, or not before.
+    It also implicitly (when combined with minlenp) tells us how many
+    characters must match before the string we are searching for.
+    Likewise when combined with minlenp and the length of the string it
+    tells us how many characters must appear after the string we have
+    found.
+
+  - max_offset
+    Only used for floating strings. This is the rightmost point that
+    the string can appear at. If set to SSize_t_MAX it indicates that the
+    string can occur infinitely far to the right.
+
+  - minlenp
+    A pointer to the minimum number of characters of the pattern that the
+    string was found inside. This is important as in the case of positive
+    lookahead or positive lookbehind we can have multiple patterns
+    involved. Consider
+
+    /(?=FOO).*F/
+
+    The minimum length of the pattern overall is 3, the minimum length
+    of the lookahead part is 3, but the minimum length of the part that
+    will actually match is 1. So 'FOO's minimum length is 3, but the
+    minimum length for the F is 1. This is important as the minimum length
+    is used to determine offsets in front of and behind the string being
+    looked for.  Since strings can be composites this is the length of the
+    pattern at the time it was committed with a scan_commit. Note that
+    the length is calculated by study_chunk, so that the minimum lengths
+    are not known until the full pattern has been compiled, thus the
+    pointer to the value.
+
+  - lookbehind
+
+    In the case of lookbehind the string being searched for can be
+    offset past the start point of the final matching string.
+    If this value was just blithely removed from the min_offset it would
+    invalidate some of the calculations for how many chars must match
+    before or after (as they are derived from min_offset and minlen and
+    the length of the string being searched for).
+    When the final pattern is compiled and the data is moved from the
+    scan_data_t structure into the regexp structure the information
+    about lookbehind is factored in, with the information that would
+    have been lost precalculated in the end_shift field for the
+    associated string.
+
+  The fields pos_min and pos_delta are used to store the minimum offset
+  and the delta to the maximum offset at the current point in the pattern.
+
+*/
+
+typedef struct scan_data_t {
+    /*I32 len_min;      unused */
+    /*I32 len_delta;    unused */
+    SSize_t pos_min;
+    SSize_t pos_delta;
+    SV *last_found;
+    SSize_t last_end;      /* min value, <0 unless valid. */
+    SSize_t last_start_min;
+    SSize_t last_start_max;
+    SV **longest;          /* Either &l_fixed, or &l_float. */
+    SV *longest_fixed;      /* longest fixed string found in pattern */
+    SSize_t offset_fixed;   /* offset where it starts */
+    SSize_t *minlen_fixed;  /* pointer to the minlen relevant to the string */
+    I32 lookbehind_fixed;   /* is the position of the string modfied by LB */
+    SV *longest_float;      /* longest floating string found in pattern */
+    SSize_t offset_float_min; /* earliest point in string it can appear */
+    SSize_t offset_float_max; /* latest point in string it can appear */
+    SSize_t *minlen_float;  /* pointer to the minlen relevant to the string */
+    SSize_t lookbehind_float; /* is the pos of the string modified by LB */
+    I32 flags;
+    I32 whilem_c;
+    SSize_t *last_closep;
+    regnode_ssc *start_class;
+} scan_data_t;
+
+/* The below is perhaps overboard, but this allows us to save a test at the
+ * expense of a mask.  This is because on both EBCDIC and ASCII machines, 'A'
+ * and 'a' differ by a single bit; the same with the upper and lower case of
+ * all other ASCII-range alphabetics.  On ASCII platforms, they are 32 apart;
+ * on EBCDIC, they are 64.  This uses an exclusive 'or' to find that bit and
+ * then inverts it to form a mask, with just a single 0, in the bit position
+ * where the upper- and lowercase differ.  XXX There are about 40 other
+ * instances in the Perl core where this micro-optimization could be used.
+ * Should decide if maintenance cost is worse, before changing those
+ *
+ * Returns a boolean as to whether or not 'v' is either a lowercase or
+ * uppercase instance of 'c', where 'c' is in [A-Za-z].  If 'c' is a
+ * compile-time constant, the generated code is better than some optimizing
+ * compilers figure out, amounting to a mask and test.  The results are
+ * meaningless if 'c' is not one of [A-Za-z] */
+#define isARG2_lower_or_UPPER_ARG1(c, v) \
+                              (((v) & ~('A' ^ 'a')) ==  ((c) & ~('A' ^ 'a')))
+
+/*
+ * Forward declarations for pregcomp()'s friends.
+ */
+
+static const scan_data_t zero_scan_data =
+  { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ,0};
+
+#define SF_BEFORE_EOL          (SF_BEFORE_SEOL|SF_BEFORE_MEOL)
+#define SF_BEFORE_SEOL         0x0001
+#define SF_BEFORE_MEOL         0x0002
+#define SF_FIX_BEFORE_EOL      (SF_FIX_BEFORE_SEOL|SF_FIX_BEFORE_MEOL)
+#define SF_FL_BEFORE_EOL       (SF_FL_BEFORE_SEOL|SF_FL_BEFORE_MEOL)
+
+#define SF_FIX_SHIFT_EOL       (+2)
+#define SF_FL_SHIFT_EOL                (+4)
+
+#define SF_FIX_BEFORE_SEOL     (SF_BEFORE_SEOL << SF_FIX_SHIFT_EOL)
+#define SF_FIX_BEFORE_MEOL     (SF_BEFORE_MEOL << SF_FIX_SHIFT_EOL)
+
+#define SF_FL_BEFORE_SEOL      (SF_BEFORE_SEOL << SF_FL_SHIFT_EOL)
+#define SF_FL_BEFORE_MEOL      (SF_BEFORE_MEOL << SF_FL_SHIFT_EOL) /* 0x20 */
+#define SF_IS_INF              0x0040
+#define SF_HAS_PAR             0x0080
+#define SF_IN_PAR              0x0100
+#define SF_HAS_EVAL            0x0200
+#define SCF_DO_SUBSTR          0x0400
+#define SCF_DO_STCLASS_AND     0x0800
+#define SCF_DO_STCLASS_OR      0x1000
+#define SCF_DO_STCLASS         (SCF_DO_STCLASS_AND|SCF_DO_STCLASS_OR)
+#define SCF_WHILEM_VISITED_POS 0x2000
+
+#define SCF_TRIE_RESTUDY        0x4000 /* Do restudy? */
+#define SCF_SEEN_ACCEPT         0x8000
+#define SCF_TRIE_DOING_RESTUDY 0x10000
+
+#define UTF cBOOL(RExC_utf8)
+
+/* The enums for all these are ordered so things work out correctly */
+#define LOC (get_regex_charset(RExC_flags) == REGEX_LOCALE_CHARSET)
+#define DEPENDS_SEMANTICS (get_regex_charset(RExC_flags)                    \
+                                                     == REGEX_DEPENDS_CHARSET)
+#define UNI_SEMANTICS (get_regex_charset(RExC_flags) == REGEX_UNICODE_CHARSET)
+#define AT_LEAST_UNI_SEMANTICS (get_regex_charset(RExC_flags)                \
+                                                     >= REGEX_UNICODE_CHARSET)
+#define ASCII_RESTRICTED (get_regex_charset(RExC_flags)                      \
+                                            == REGEX_ASCII_RESTRICTED_CHARSET)
+#define AT_LEAST_ASCII_RESTRICTED (get_regex_charset(RExC_flags)             \
+                                            >= REGEX_ASCII_RESTRICTED_CHARSET)
+#define ASCII_FOLD_RESTRICTED (get_regex_charset(RExC_flags)                 \
+                                        == REGEX_ASCII_MORE_RESTRICTED_CHARSET)
+
+#define FOLD cBOOL(RExC_flags & RXf_PMf_FOLD)
+
+/* For programs that want to be strictly Unicode compatible by dying if any
+ * attempt is made to match a non-Unicode code point against a Unicode
+ * property.  */
+#define ALWAYS_WARN_SUPER  ckDEAD(packWARN(WARN_NON_UNICODE))
+
+#define OOB_NAMEDCLASS         -1
+
+/* There is no code point that is out-of-bounds, so this is problematic.  But
+ * its only current use is to initialize a variable that is always set before
+ * looked at. */
+#define OOB_UNICODE            0xDEADBEEF
+
+#define CHR_SVLEN(sv) (UTF ? sv_len_utf8(sv) : SvCUR(sv))
+#define CHR_DIST(a,b) (UTF ? utf8_distance(a,b) : a - b)
+
+
+/* length of regex to show in messages that don't mark a position within */
+#define RegexLengthToShowInErrorMessages 127
+
+/*
+ * If MARKER[12] are adjusted, be sure to adjust the constants at the top
+ * of t/op/regmesg.t, the tests in t/op/re_tests, and those in
+ * op/pragma/warn/regcomp.
+ */
+#define MARKER1 "<-- HERE"    /* marker as it appears in the description */
+#define MARKER2 " <-- HERE "  /* marker as it appears within the regex */
+
+#define REPORT_LOCATION " in regex; marked by " MARKER1    \
+                        " in m/%"UTF8f MARKER2 "%"UTF8f"/"
+
+#define REPORT_LOCATION_ARGS(offset)            \
+                UTF8fARG(UTF, offset, RExC_precomp), \
+                UTF8fARG(UTF, RExC_end - RExC_precomp - offset, RExC_precomp + offset)
+
+/*
+ * Calls SAVEDESTRUCTOR_X if needed, then calls Perl_croak with the given
+ * arg. Show regex, up to a maximum length. If it's too long, chop and add
+ * "...".
+ */
+#define _FAIL(code) STMT_START {                                       \
+    const char *ellipses = "";                                         \
+    IV len = RExC_end - RExC_precomp;                                  \
+                                                                       \
+    if (!SIZE_ONLY)                                                    \
+       SAVEFREESV(RExC_rx_sv);                                         \
+    if (len > RegexLengthToShowInErrorMessages) {                      \
+       /* chop 10 shorter than the max, to ensure meaning of "..." */  \
+       len = RegexLengthToShowInErrorMessages - 10;                    \
+       ellipses = "...";                                               \
+    }                                                                  \
+    code;                                                               \
+} STMT_END
+
+#define        FAIL(msg) _FAIL(                            \
+    Perl_croak(aTHX_ "%s in regex m/%"UTF8f"%s/",          \
+           msg, UTF8fARG(UTF, len, RExC_precomp), ellipses))
+
+#define        FAIL2(msg,arg) _FAIL(                       \
+    Perl_croak(aTHX_ msg " in regex m/%"UTF8f"%s/",        \
+           arg, UTF8fARG(UTF, len, RExC_precomp), ellipses))
+
+/*
+ * Simple_vFAIL -- like FAIL, but marks the current location in the scan
+ */
+#define        Simple_vFAIL(m) STMT_START {                                    \
+    const IV offset = RExC_parse - RExC_precomp;                       \
+    Perl_croak(aTHX_ "%s" REPORT_LOCATION,                             \
+           m, REPORT_LOCATION_ARGS(offset));   \
+} STMT_END
+
+/*
+ * Calls SAVEDESTRUCTOR_X if needed, then Simple_vFAIL()
+ */
+#define        vFAIL(m) STMT_START {                           \
+    if (!SIZE_ONLY)                                    \
+       SAVEFREESV(RExC_rx_sv);                         \
+    Simple_vFAIL(m);                                   \
+} STMT_END
+
+/*
+ * Like Simple_vFAIL(), but accepts two arguments.
+ */
+#define        Simple_vFAIL2(m,a1) STMT_START {                        \
+    const IV offset = RExC_parse - RExC_precomp;                       \
+    S_re_croak2(aTHX_ UTF, m, REPORT_LOCATION, a1,                     \
+                      REPORT_LOCATION_ARGS(offset));   \
+} STMT_END
+
+/*
+ * Calls SAVEDESTRUCTOR_X if needed, then Simple_vFAIL2().
+ */
+#define        vFAIL2(m,a1) STMT_START {                       \
+    if (!SIZE_ONLY)                                    \
+       SAVEFREESV(RExC_rx_sv);                         \
+    Simple_vFAIL2(m, a1);                              \
+} STMT_END
+
+
+/*
+ * Like Simple_vFAIL(), but accepts three arguments.
+ */
+#define        Simple_vFAIL3(m, a1, a2) STMT_START {                   \
+    const IV offset = RExC_parse - RExC_precomp;               \
+    S_re_croak2(aTHX_ UTF, m, REPORT_LOCATION, a1, a2,         \
+           REPORT_LOCATION_ARGS(offset));      \
+} STMT_END
+
+/*
+ * Calls SAVEDESTRUCTOR_X if needed, then Simple_vFAIL3().
+ */
+#define        vFAIL3(m,a1,a2) STMT_START {                    \
+    if (!SIZE_ONLY)                                    \
+       SAVEFREESV(RExC_rx_sv);                         \
+    Simple_vFAIL3(m, a1, a2);                          \
+} STMT_END
+
+/*
+ * Like Simple_vFAIL(), but accepts four arguments.
+ */
+#define        Simple_vFAIL4(m, a1, a2, a3) STMT_START {               \
+    const IV offset = RExC_parse - RExC_precomp;               \
+    S_re_croak2(aTHX_ UTF, m, REPORT_LOCATION, a1, a2, a3,             \
+           REPORT_LOCATION_ARGS(offset));      \
+} STMT_END
+
+#define        vFAIL4(m,a1,a2,a3) STMT_START {                 \
+    if (!SIZE_ONLY)                                    \
+       SAVEFREESV(RExC_rx_sv);                         \
+    Simple_vFAIL4(m, a1, a2, a3);                      \
+} STMT_END
+
+/* A specialized version of vFAIL2 that works with UTF8f */
+#define vFAIL2utf8f(m, a1) STMT_START { \
+    const IV offset = RExC_parse - RExC_precomp;   \
+    if (!SIZE_ONLY)                                \
+        SAVEFREESV(RExC_rx_sv);                    \
+    S_re_croak2(aTHX_ UTF, m, REPORT_LOCATION, a1, \
+            REPORT_LOCATION_ARGS(offset));         \
+} STMT_END
+
+
+/* m is not necessarily a "literal string", in this macro */
+#define reg_warn_non_literal_string(loc, m) STMT_START {                \
+    const IV offset = loc - RExC_precomp;                               \
+    Perl_warner(aTHX_ packWARN(WARN_REGEXP), "%s" REPORT_LOCATION,      \
+            m, REPORT_LOCATION_ARGS(offset));       \
+} STMT_END
+
+#define        ckWARNreg(loc,m) STMT_START {                                   \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,     \
+           REPORT_LOCATION_ARGS(offset));              \
+} STMT_END
+
+#define        vWARN_dep(loc, m) STMT_START {                                  \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_warner(aTHX_ packWARN(WARN_DEPRECATED), m REPORT_LOCATION,    \
+           REPORT_LOCATION_ARGS(offset));              \
+} STMT_END
+
+#define        ckWARNdep(loc,m) STMT_START {                                   \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_ck_warner_d(aTHX_ packWARN(WARN_DEPRECATED),                  \
+           m REPORT_LOCATION,                                          \
+           REPORT_LOCATION_ARGS(offset));              \
+} STMT_END
+
+#define        ckWARNregdep(loc,m) STMT_START {                                \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_ck_warner_d(aTHX_ packWARN2(WARN_DEPRECATED, WARN_REGEXP),    \
+           m REPORT_LOCATION,                                          \
+           REPORT_LOCATION_ARGS(offset));              \
+} STMT_END
+
+#define        ckWARN2reg_d(loc,m, a1) STMT_START {                            \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_ck_warner_d(aTHX_ packWARN(WARN_REGEXP),                      \
+           m REPORT_LOCATION,                                          \
+           a1, REPORT_LOCATION_ARGS(offset));  \
+} STMT_END
+
+#define        ckWARN2reg(loc, m, a1) STMT_START {                             \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,     \
+           a1, REPORT_LOCATION_ARGS(offset));  \
+} STMT_END
+
+#define        vWARN3(loc, m, a1, a2) STMT_START {                             \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,                \
+           a1, a2, REPORT_LOCATION_ARGS(offset));      \
+} STMT_END
+
+#define        ckWARN3reg(loc, m, a1, a2) STMT_START {                         \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,     \
+           a1, a2, REPORT_LOCATION_ARGS(offset));      \
+} STMT_END
+
+#define        vWARN4(loc, m, a1, a2, a3) STMT_START {                         \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,                \
+           a1, a2, a3, REPORT_LOCATION_ARGS(offset)); \
+} STMT_END
+
+#define        ckWARN4reg(loc, m, a1, a2, a3) STMT_START {                     \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_ck_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,     \
+           a1, a2, a3, REPORT_LOCATION_ARGS(offset)); \
+} STMT_END
+
+#define        vWARN5(loc, m, a1, a2, a3, a4) STMT_START {                     \
+    const IV offset = loc - RExC_precomp;                              \
+    Perl_warner(aTHX_ packWARN(WARN_REGEXP), m REPORT_LOCATION,                \
+           a1, a2, a3, a4, REPORT_LOCATION_ARGS(offset)); \
+} STMT_END
+
+
+/* Allow for side effects in s */
+#define REGC(c,s) STMT_START {                 \
+    if (!SIZE_ONLY) *(s) = (c); else (void)(s);        \
+} STMT_END
+
+/* Macros for recording node offsets.   20001227 mjd@plover.com
+ * Nodes are numbered 1, 2, 3, 4.  Node #n's position is recorded in
+ * element 2*n-1 of the array.  Element #2n holds the byte length node #n.
+ * Element 0 holds the number n.
+ * Position is 1 indexed.
+ */
+#ifndef RE_TRACK_PATTERN_OFFSETS
+#define Set_Node_Offset_To_R(node,byte)
+#define Set_Node_Offset(node,byte)
+#define Set_Cur_Node_Offset
+#define Set_Node_Length_To_R(node,len)
+#define Set_Node_Length(node,len)
+#define Set_Node_Cur_Length(node,start)
+#define Node_Offset(n)
+#define Node_Length(n)
+#define Set_Node_Offset_Length(node,offset,len)
+#define ProgLen(ri) ri->u.proglen
+#define SetProgLen(ri,x) ri->u.proglen = x
+#else
+#define ProgLen(ri) ri->u.offsets[0]
+#define SetProgLen(ri,x) ri->u.offsets[0] = x
+#define Set_Node_Offset_To_R(node,byte) STMT_START {                   \
+    if (! SIZE_ONLY) {                                                 \
+       MJD_OFFSET_DEBUG(("** (%d) offset of node %d is %d.\n",         \
+                   __LINE__, (int)(node), (int)(byte)));               \
+       if((node) < 0) {                                                \
+           Perl_croak(aTHX_ "value of node is %d in Offset macro",     \
+                                         (int)(node));                  \
+       } else {                                                        \
+           RExC_offsets[2*(node)-1] = (byte);                          \
+       }                                                               \
+    }                                                                  \
+} STMT_END
+
+#define Set_Node_Offset(node,byte) \
+    Set_Node_Offset_To_R((node)-RExC_emit_start, (byte)-RExC_start)
+#define Set_Cur_Node_Offset Set_Node_Offset(RExC_emit, RExC_parse)
+
+#define Set_Node_Length_To_R(node,len) STMT_START {                    \
+    if (! SIZE_ONLY) {                                                 \
+       MJD_OFFSET_DEBUG(("** (%d) size of node %d is %d.\n",           \
+               __LINE__, (int)(node), (int)(len)));                    \
+       if((node) < 0) {                                                \
+           Perl_croak(aTHX_ "value of node is %d in Length macro",     \
+                                         (int)(node));                  \
+       } else {                                                        \
+           RExC_offsets[2*(node)] = (len);                             \
+       }                                                               \
+    }                                                                  \
+} STMT_END
+
+#define Set_Node_Length(node,len) \
+    Set_Node_Length_To_R((node)-RExC_emit_start, len)
+#define Set_Node_Cur_Length(node, start)                \
+    Set_Node_Length(node, RExC_parse - start)
+
+/* Get offsets and lengths */
+#define Node_Offset(n) (RExC_offsets[2*((n)-RExC_emit_start)-1])
+#define Node_Length(n) (RExC_offsets[2*((n)-RExC_emit_start)])
+
+#define Set_Node_Offset_Length(node,offset,len) STMT_START {   \
+    Set_Node_Offset_To_R((node)-RExC_emit_start, (offset));    \
+    Set_Node_Length_To_R((node)-RExC_emit_start, (len));       \
+} STMT_END
+#endif
+
+#if PERL_ENABLE_EXPERIMENTAL_REGEX_OPTIMISATIONS
+#define EXPERIMENTAL_INPLACESCAN
+#endif /*PERL_ENABLE_EXPERIMENTAL_REGEX_OPTIMISATIONS*/
+
+#define DEBUG_RExC_seen() \
+        DEBUG_OPTIMISE_MORE_r({                                             \
+            PerlIO_printf(Perl_debug_log,"RExC_seen: ");                    \
+                                                                            \
+            if (RExC_seen & REG_ZERO_LEN_SEEN)                              \
+                PerlIO_printf(Perl_debug_log,"REG_ZERO_LEN_SEEN ");         \
+                                                                            \
+            if (RExC_seen & REG_LOOKBEHIND_SEEN)                            \
+                PerlIO_printf(Perl_debug_log,"REG_LOOKBEHIND_SEEN ");       \
+                                                                            \
+            if (RExC_seen & REG_GPOS_SEEN)                                  \
+                PerlIO_printf(Perl_debug_log,"REG_GPOS_SEEN ");             \
+                                                                            \
+            if (RExC_seen & REG_CANY_SEEN)                                  \
+                PerlIO_printf(Perl_debug_log,"REG_CANY_SEEN ");             \
+                                                                            \
+            if (RExC_seen & REG_RECURSE_SEEN)                               \
+                PerlIO_printf(Perl_debug_log,"REG_RECURSE_SEEN ");          \
+                                                                            \
+            if (RExC_seen & REG_TOP_LEVEL_BRANCHES_SEEN)                         \
+                PerlIO_printf(Perl_debug_log,"REG_TOP_LEVEL_BRANCHES_SEEN ");    \
+                                                                            \
+            if (RExC_seen & REG_VERBARG_SEEN)                               \
+                PerlIO_printf(Perl_debug_log,"REG_VERBARG_SEEN ");          \
+                                                                            \
+            if (RExC_seen & REG_CUTGROUP_SEEN)                              \
+                PerlIO_printf(Perl_debug_log,"REG_CUTGROUP_SEEN ");         \
+                                                                            \
+            if (RExC_seen & REG_RUN_ON_COMMENT_SEEN)                        \
+                PerlIO_printf(Perl_debug_log,"REG_RUN_ON_COMMENT_SEEN ");   \
+                                                                            \
+            if (RExC_seen & REG_UNFOLDED_MULTI_SEEN)                        \
+                PerlIO_printf(Perl_debug_log,"REG_UNFOLDED_MULTI_SEEN ");   \
+                                                                            \
+            if (RExC_seen & REG_GOSTART_SEEN)                               \
+                PerlIO_printf(Perl_debug_log,"REG_GOSTART_SEEN ");          \
+                                                                            \
+            if (RExC_seen & REG_UNBOUNDED_QUANTIFIER_SEEN)                               \
+                PerlIO_printf(Perl_debug_log,"REG_UNBOUNDED_QUANTIFIER_SEEN ");          \
+                                                                            \
+            PerlIO_printf(Perl_debug_log,"\n");                             \
+        });
+
+#define DEBUG_STUDYDATA(str,data,depth)                              \
+DEBUG_OPTIMISE_MORE_r(if(data){                                      \
+    PerlIO_printf(Perl_debug_log,                                    \
+        "%*s" str "Pos:%"IVdf"/%"IVdf                                \
+        " Flags: 0x%"UVXf" Whilem_c: %"IVdf" Lcp: %"IVdf" %s",       \
+        (int)(depth)*2, "",                                          \
+        (IV)((data)->pos_min),                                       \
+        (IV)((data)->pos_delta),                                     \
+        (UV)((data)->flags),                                         \
+        (IV)((data)->whilem_c),                                      \
+        (IV)((data)->last_closep ? *((data)->last_closep) : -1),     \
+        is_inf ? "INF " : ""                                         \
+    );                                                               \
+    if ((data)->last_found)                                          \
+        PerlIO_printf(Perl_debug_log,                                \
+            "Last:'%s' %"IVdf":%"IVdf"/%"IVdf" %sFixed:'%s' @ %"IVdf \
+            " %sFloat: '%s' @ %"IVdf"/%"IVdf"",                      \
+            SvPVX_const((data)->last_found),                         \
+            (IV)((data)->last_end),                                  \
+            (IV)((data)->last_start_min),                            \
+            (IV)((data)->last_start_max),                            \
+            ((data)->longest &&                                      \
+             (data)->longest==&((data)->longest_fixed)) ? "*" : "",  \
+            SvPVX_const((data)->longest_fixed),                      \
+            (IV)((data)->offset_fixed),                              \
+            ((data)->longest &&                                      \
+             (data)->longest==&((data)->longest_float)) ? "*" : "",  \
+            SvPVX_const((data)->longest_float),                      \
+            (IV)((data)->offset_float_min),                          \
+            (IV)((data)->offset_float_max)                           \
+        );                                                           \
+    PerlIO_printf(Perl_debug_log,"\n");                              \
+});
+
+/* Mark that we cannot extend a found fixed substring at this point.
+   Update the longest found anchored substring and the longest found
+   floating substrings if needed. */
+
+STATIC void
+S_scan_commit(pTHX_ const RExC_state_t *pRExC_state, scan_data_t *data,
+                    SSize_t *minlenp, int is_inf)
+{
+    const STRLEN l = CHR_SVLEN(data->last_found);
+    const STRLEN old_l = CHR_SVLEN(*data->longest);
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_SCAN_COMMIT;
+
+    if ((l >= old_l) && ((l > old_l) || (data->flags & SF_BEFORE_EOL))) {
+       SvSetMagicSV(*data->longest, data->last_found);
+       if (*data->longest == data->longest_fixed) {
+           data->offset_fixed = l ? data->last_start_min : data->pos_min;
+           if (data->flags & SF_BEFORE_EOL)
+               data->flags
+                   |= ((data->flags & SF_BEFORE_EOL) << SF_FIX_SHIFT_EOL);
+           else
+               data->flags &= ~SF_FIX_BEFORE_EOL;
+           data->minlen_fixed=minlenp;
+           data->lookbehind_fixed=0;
+       }
+       else { /* *data->longest == data->longest_float */
+           data->offset_float_min = l ? data->last_start_min : data->pos_min;
+           data->offset_float_max = (l
+                                     ? data->last_start_max
+                                     : (data->pos_delta == SSize_t_MAX
+                                        ? SSize_t_MAX
+                                        : data->pos_min + data->pos_delta));
+           if (is_inf
+                || (STRLEN)data->offset_float_max > (STRLEN)SSize_t_MAX)
+               data->offset_float_max = SSize_t_MAX;
+           if (data->flags & SF_BEFORE_EOL)
+               data->flags
+                   |= ((data->flags & SF_BEFORE_EOL) << SF_FL_SHIFT_EOL);
+           else
+               data->flags &= ~SF_FL_BEFORE_EOL;
+            data->minlen_float=minlenp;
+            data->lookbehind_float=0;
+       }
+    }
+    SvCUR_set(data->last_found, 0);
+    {
+       SV * const sv = data->last_found;
+       if (SvUTF8(sv) && SvMAGICAL(sv)) {
+           MAGIC * const mg = mg_find(sv, PERL_MAGIC_utf8);
+           if (mg)
+               mg->mg_len = 0;
+       }
+    }
+    data->last_end = -1;
+    data->flags &= ~SF_BEFORE_EOL;
+    DEBUG_STUDYDATA("commit: ",data,0);
+}
+
+/* An SSC is just a regnode_charclass_posix with an extra field: the inversion
+ * list that describes which code points it matches */
+
+STATIC void
+S_ssc_anything(pTHX_ regnode_ssc *ssc)
+{
+    /* Set the SSC 'ssc' to match an empty string or any code point */
+
+    PERL_ARGS_ASSERT_SSC_ANYTHING;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    ssc->invlist = sv_2mortal(_new_invlist(2)); /* mortalize so won't leak */
+    _append_range_to_invlist(ssc->invlist, 0, UV_MAX);
+    ANYOF_FLAGS(ssc) |= ANYOF_EMPTY_STRING;    /* Plus match empty string */
+}
+
+STATIC int
+S_ssc_is_anything(pTHX_ const regnode_ssc *ssc)
+{
+    /* Returns TRUE if the SSC 'ssc' can match the empty string and any code
+     * point; FALSE otherwise.  Thus, this is used to see if using 'ssc' buys
+     * us anything: if the function returns TRUE, 'ssc' hasn't been restricted
+     * in any way, so there's no point in using it */
+
+    UV start, end;
+    bool ret;
+
+    PERL_ARGS_ASSERT_SSC_IS_ANYTHING;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    if (! (ANYOF_FLAGS(ssc) & ANYOF_EMPTY_STRING)) {
+        return FALSE;
+    }
+
+    /* See if the list consists solely of the range 0 - Infinity */
+    invlist_iterinit(ssc->invlist);
+    ret = invlist_iternext(ssc->invlist, &start, &end)
+          && start == 0
+          && end == UV_MAX;
+
+    invlist_iterfinish(ssc->invlist);
+
+    if (ret) {
+        return TRUE;
+    }
+
+    /* If e.g., both \w and \W are set, matches everything */
+    if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)) {
+        int i;
+        for (i = 0; i < ANYOF_POSIXL_MAX; i += 2) {
+            if (ANYOF_POSIXL_TEST(ssc, i) && ANYOF_POSIXL_TEST(ssc, i+1)) {
+                return TRUE;
+            }
+        }
+    }
+
+    return FALSE;
+}
+
+STATIC void
+S_ssc_init(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc)
+{
+    /* Initializes the SSC 'ssc'.  This includes setting it to match an empty
+     * string, any code point, or any posix class under locale */
+
+    PERL_ARGS_ASSERT_SSC_INIT;
+
+    Zero(ssc, 1, regnode_ssc);
+    set_ANYOF_SYNTHETIC(ssc);
+    ARG_SET(ssc, ANYOF_NONBITMAP_EMPTY);
+    ssc_anything(ssc);
+
+    /* If any portion of the regex is to operate under locale rules,
+     * initialization includes it.  The reason this isn't done for all regexes
+     * is that the optimizer was written under the assumption that locale was
+     * all-or-nothing.  Given the complexity and lack of documentation in the
+     * optimizer, and that there are inadequate test cases for locale, many
+     * parts of it may not work properly, it is safest to avoid locale unless
+     * necessary. */
+    if (RExC_contains_locale) {
+       ANYOF_POSIXL_SETALL(ssc);
+    }
+    else {
+       ANYOF_POSIXL_ZERO(ssc);
+    }
+}
+
+STATIC int
+S_ssc_is_cp_posixl_init(pTHX_ const RExC_state_t *pRExC_state,
+                              const regnode_ssc *ssc)
+{
+    /* Returns TRUE if the SSC 'ssc' is in its initial state with regard only
+     * to the list of code points matched, and locale posix classes; hence does
+     * not check its flags) */
+
+    UV start, end;
+    bool ret;
+
+    PERL_ARGS_ASSERT_SSC_IS_CP_POSIXL_INIT;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    invlist_iterinit(ssc->invlist);
+    ret = invlist_iternext(ssc->invlist, &start, &end)
+          && start == 0
+          && end == UV_MAX;
+
+    invlist_iterfinish(ssc->invlist);
+
+    if (! ret) {
+        return FALSE;
+    }
+
+    if (RExC_contains_locale && ! ANYOF_POSIXL_SSC_TEST_ALL_SET(ssc)) {
+        return FALSE;
+    }
+
+    return TRUE;
+}
+
+STATIC SV*
+S_get_ANYOF_cp_list_for_ssc(pTHX_ const RExC_state_t *pRExC_state,
+                               const regnode_charclass* const node)
+{
+    /* Returns a mortal inversion list defining which code points are matched
+     * by 'node', which is of type ANYOF.  Handles complementing the result if
+     * appropriate.  If some code points aren't knowable at this time, the
+     * returned list must, and will, contain every code point that is a
+     * possibility. */
+
+    SV* invlist = sv_2mortal(_new_invlist(0));
+    SV* only_utf8_locale_invlist = NULL;
+    unsigned int i;
+    const U32 n = ARG(node);
+    bool new_node_has_latin1 = FALSE;
+
+    PERL_ARGS_ASSERT_GET_ANYOF_CP_LIST_FOR_SSC;
+
+    /* Look at the data structure created by S_set_ANYOF_arg() */
+    if (n != ANYOF_NONBITMAP_EMPTY) {
+        SV * const rv = MUTABLE_SV(RExC_rxi->data->data[n]);
+        AV * const av = MUTABLE_AV(SvRV(rv));
+        SV **const ary = AvARRAY(av);
+        assert(RExC_rxi->data->what[n] == 's');
+
+        if (ary[1] && ary[1] != &PL_sv_undef) { /* Has compile-time swash */
+            invlist = sv_2mortal(invlist_clone(_get_swash_invlist(ary[1])));
+        }
+        else if (ary[0] && ary[0] != &PL_sv_undef) {
+
+            /* Here, no compile-time swash, and there are things that won't be
+             * known until runtime -- we have to assume it could be anything */
+            return _add_range_to_invlist(invlist, 0, UV_MAX);
+        }
+        else if (ary[3] && ary[3] != &PL_sv_undef) {
+
+            /* Here no compile-time swash, and no run-time only data.  Use the
+             * node's inversion list */
+            invlist = sv_2mortal(invlist_clone(ary[3]));
+        }
+
+        /* Get the code points valid only under UTF-8 locales */
+        if ((ANYOF_FLAGS(node) & ANYOF_LOC_FOLD)
+            && ary[2] && ary[2] != &PL_sv_undef)
+        {
+            only_utf8_locale_invlist = ary[2];
+        }
+    }
+
+    /* An ANYOF node contains a bitmap for the first 256 code points, and an
+     * inversion list for the others, but if there are code points that should
+     * match only conditionally on the target string being UTF-8, those are
+     * placed in the inversion list, and not the bitmap.  Since there are
+     * circumstances under which they could match, they are included in the
+     * SSC.  But if the ANYOF node is to be inverted, we have to exclude them
+     * here, so that when we invert below, the end result actually does include
+     * them.  (Think about "\xe0" =~ /[^\xc0]/di;).  We have to do this here
+     * before we add the unconditionally matched code points */
+    if (ANYOF_FLAGS(node) & ANYOF_INVERT) {
+        _invlist_intersection_complement_2nd(invlist,
+                                             PL_UpperLatin1,
+                                             &invlist);
+    }
+
+    /* Add in the points from the bit map */
+    for (i = 0; i < 256; i++) {
+        if (ANYOF_BITMAP_TEST(node, i)) {
+            invlist = add_cp_to_invlist(invlist, i);
+            new_node_has_latin1 = TRUE;
+        }
+    }
+
+    /* If this can match all upper Latin1 code points, have to add them
+     * as well */
+    if (ANYOF_FLAGS(node) & ANYOF_NON_UTF8_NON_ASCII_ALL) {
+        _invlist_union(invlist, PL_UpperLatin1, &invlist);
+    }
+
+    /* Similarly for these */
+    if (ANYOF_FLAGS(node) & ANYOF_ABOVE_LATIN1_ALL) {
+        invlist = _add_range_to_invlist(invlist, 256, UV_MAX);
+    }
+
+    if (ANYOF_FLAGS(node) & ANYOF_INVERT) {
+        _invlist_invert(invlist);
+    }
+    else if (new_node_has_latin1 && ANYOF_FLAGS(node) & ANYOF_LOC_FOLD) {
+
+        /* Under /li, any 0-255 could fold to any other 0-255, depending on the
+         * locale.  We can skip this if there are no 0-255 at all. */
+        _invlist_union(invlist, PL_Latin1, &invlist);
+    }
+
+    /* Similarly add the UTF-8 locale possible matches.  These have to be
+     * deferred until after the non-UTF-8 locale ones are taken care of just
+     * above, or it leads to wrong results under ANYOF_INVERT */
+    if (only_utf8_locale_invlist) {
+        _invlist_union_maybe_complement_2nd(invlist,
+                                            only_utf8_locale_invlist,
+                                            ANYOF_FLAGS(node) & ANYOF_INVERT,
+                                            &invlist);
+    }
+
+    return invlist;
+}
+
+/* These two functions currently do the exact same thing */
+#define ssc_init_zero          ssc_init
+
+#define ssc_add_cp(ssc, cp)   ssc_add_range((ssc), (cp), (cp))
+#define ssc_match_all_cp(ssc) ssc_add_range(ssc, 0, UV_MAX)
+
+/* 'AND' a given class with another one.  Can create false positives.  'ssc'
+ * should not be inverted.  'and_with->flags & ANYOF_POSIXL' should be 0 if
+ * 'and_with' is a regnode_charclass instead of a regnode_ssc. */
+
+STATIC void
+S_ssc_and(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
+                const regnode_charclass *and_with)
+{
+    /* Accumulate into SSC 'ssc' its 'AND' with 'and_with', which is either
+     * another SSC or a regular ANYOF class.  Can create false positives. */
+
+    SV* anded_cp_list;
+    U8  anded_flags;
+
+    PERL_ARGS_ASSERT_SSC_AND;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    /* 'and_with' is used as-is if it too is an SSC; otherwise have to extract
+     * the code point inversion list and just the relevant flags */
+    if (is_ANYOF_SYNTHETIC(and_with)) {
+        anded_cp_list = ((regnode_ssc *)and_with)->invlist;
+        anded_flags = ANYOF_FLAGS(and_with);
+
+        /* XXX This is a kludge around what appears to be deficiencies in the
+         * optimizer.  If we make S_ssc_anything() add in the WARN_SUPER flag,
+         * there are paths through the optimizer where it doesn't get weeded
+         * out when it should.  And if we don't make some extra provision for
+         * it like the code just below, it doesn't get added when it should.
+         * This solution is to add it only when AND'ing, which is here, and
+         * only when what is being AND'ed is the pristine, original node
+         * matching anything.  Thus it is like adding it to ssc_anything() but
+         * only when the result is to be AND'ed.  Probably the same solution
+         * could be adopted for the same problem we have with /l matching,
+         * which is solved differently in S_ssc_init(), and that would lead to
+         * fewer false positives than that solution has.  But if this solution
+         * creates bugs, the consequences are only that a warning isn't raised
+         * that should be; while the consequences for having /l bugs is
+         * incorrect matches */
+        if (ssc_is_anything((regnode_ssc *)and_with)) {
+            anded_flags |= ANYOF_WARN_SUPER;
+        }
+    }
+    else {
+        anded_cp_list = get_ANYOF_cp_list_for_ssc(pRExC_state, and_with);
+        anded_flags = ANYOF_FLAGS(and_with) & ANYOF_COMMON_FLAGS;
+    }
+
+    ANYOF_FLAGS(ssc) &= anded_flags;
+
+    /* Below, C1 is the list of code points in 'ssc'; P1, its posix classes.
+     * C2 is the list of code points in 'and-with'; P2, its posix classes.
+     * 'and_with' may be inverted.  When not inverted, we have the situation of
+     * computing:
+     *  (C1 | P1) & (C2 | P2)
+     *                     =  (C1 & (C2 | P2)) | (P1 & (C2 | P2))
+     *                     =  ((C1 & C2) | (C1 & P2)) | ((P1 & C2) | (P1 & P2))
+     *                    <=  ((C1 & C2) |       P2)) | ( P1       | (P1 & P2))
+     *                    <=  ((C1 & C2) | P1 | P2)
+     * Alternatively, the last few steps could be:
+     *                     =  ((C1 & C2) | (C1 & P2)) | ((P1 & C2) | (P1 & P2))
+     *                    <=  ((C1 & C2) |  C1      ) | (      C2  | (P1 & P2))
+     *                    <=  (C1 | C2 | (P1 & P2))
+     * We favor the second approach if either P1 or P2 is non-empty.  This is
+     * because these components are a barrier to doing optimizations, as what
+     * they match cannot be known until the moment of matching as they are
+     * dependent on the current locale, 'AND"ing them likely will reduce or
+     * eliminate them.
+     * But we can do better if we know that C1,P1 are in their initial state (a
+     * frequent occurrence), each matching everything:
+     *  (<everything>) & (C2 | P2) =  C2 | P2
+     * Similarly, if C2,P2 are in their initial state (again a frequent
+     * occurrence), the result is a no-op
+     *  (C1 | P1) & (<everything>) =  C1 | P1
+     *
+     * Inverted, we have
+     *  (C1 | P1) & ~(C2 | P2)  =  (C1 | P1) & (~C2 & ~P2)
+     *                          =  (C1 & (~C2 & ~P2)) | (P1 & (~C2 & ~P2))
+     *                         <=  (C1 & ~C2) | (P1 & ~P2)
+     * */
+
+    if ((ANYOF_FLAGS(and_with) & ANYOF_INVERT)
+        && ! is_ANYOF_SYNTHETIC(and_with))
+    {
+        unsigned int i;
+
+        ssc_intersection(ssc,
+                         anded_cp_list,
+                         FALSE /* Has already been inverted */
+                         );
+
+        /* If either P1 or P2 is empty, the intersection will be also; can skip
+         * the loop */
+        if (! (ANYOF_FLAGS(and_with) & ANYOF_POSIXL)) {
+            ANYOF_POSIXL_ZERO(ssc);
+        }
+        else if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)) {
+
+            /* Note that the Posix class component P from 'and_with' actually
+             * looks like:
+             *      P = Pa | Pb | ... | Pn
+             * where each component is one posix class, such as in [\w\s].
+             * Thus
+             *      ~P = ~(Pa | Pb | ... | Pn)
+             *         = ~Pa & ~Pb & ... & ~Pn
+             *        <= ~Pa | ~Pb | ... | ~Pn
+             * The last is something we can easily calculate, but unfortunately
+             * is likely to have many false positives.  We could do better
+             * in some (but certainly not all) instances if two classes in
+             * P have known relationships.  For example
+             *      :lower: <= :alpha: <= :alnum: <= \w <= :graph: <= :print:
+             * So
+             *      :lower: & :print: = :lower:
+             * And similarly for classes that must be disjoint.  For example,
+             * since \s and \w can have no elements in common based on rules in
+             * the POSIX standard,
+             *      \w & ^\S = nothing
+             * Unfortunately, some vendor locales do not meet the Posix
+             * standard, in particular almost everything by Microsoft.
+             * The loop below just changes e.g., \w into \W and vice versa */
+
+            regnode_charclass_posixl temp;
+            int add = 1;    /* To calculate the index of the complement */
+
+            ANYOF_POSIXL_ZERO(&temp);
+            for (i = 0; i < ANYOF_MAX; i++) {
+                assert(i % 2 != 0
+                       || ! ANYOF_POSIXL_TEST((regnode_charclass_posixl*) and_with, i)
+                       || ! ANYOF_POSIXL_TEST((regnode_charclass_posixl*) and_with, i + 1));
+
+                if (ANYOF_POSIXL_TEST((regnode_charclass_posixl*) and_with, i)) {
+                    ANYOF_POSIXL_SET(&temp, i + add);
+                }
+                add = 0 - add; /* 1 goes to -1; -1 goes to 1 */
+            }
+            ANYOF_POSIXL_AND(&temp, ssc);
+
+        } /* else ssc already has no posixes */
+    } /* else: Not inverted.  This routine is a no-op if 'and_with' is an SSC
+         in its initial state */
+    else if (! is_ANYOF_SYNTHETIC(and_with)
+             || ! ssc_is_cp_posixl_init(pRExC_state, (regnode_ssc *)and_with))
+    {
+        /* But if 'ssc' is in its initial state, the result is just 'and_with';
+         * copy it over 'ssc' */
+        if (ssc_is_cp_posixl_init(pRExC_state, ssc)) {
+            if (is_ANYOF_SYNTHETIC(and_with)) {
+                StructCopy(and_with, ssc, regnode_ssc);
+            }
+            else {
+                ssc->invlist = anded_cp_list;
+                ANYOF_POSIXL_ZERO(ssc);
+                if (ANYOF_FLAGS(and_with) & ANYOF_POSIXL) {
+                    ANYOF_POSIXL_OR((regnode_charclass_posixl*) and_with, ssc);
+                }
+            }
+        }
+        else if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)
+                 || (ANYOF_FLAGS(and_with) & ANYOF_POSIXL))
+        {
+            /* One or the other of P1, P2 is non-empty. */
+            if (ANYOF_FLAGS(and_with) & ANYOF_POSIXL) {
+                ANYOF_POSIXL_AND((regnode_charclass_posixl*) and_with, ssc);
+            }
+            ssc_union(ssc, anded_cp_list, FALSE);
+        }
+        else { /* P1 = P2 = empty */
+            ssc_intersection(ssc, anded_cp_list, FALSE);
+        }
+    }
+}
+
+STATIC void
+S_ssc_or(pTHX_ const RExC_state_t *pRExC_state, regnode_ssc *ssc,
+               const regnode_charclass *or_with)
+{
+    /* Accumulate into SSC 'ssc' its 'OR' with 'or_with', which is either
+     * another SSC or a regular ANYOF class.  Can create false positives if
+     * 'or_with' is to be inverted. */
+
+    SV* ored_cp_list;
+    U8 ored_flags;
+
+    PERL_ARGS_ASSERT_SSC_OR;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    /* 'or_with' is used as-is if it too is an SSC; otherwise have to extract
+     * the code point inversion list and just the relevant flags */
+    if (is_ANYOF_SYNTHETIC(or_with)) {
+        ored_cp_list = ((regnode_ssc*) or_with)->invlist;
+        ored_flags = ANYOF_FLAGS(or_with);
+    }
+    else {
+        ored_cp_list = get_ANYOF_cp_list_for_ssc(pRExC_state, or_with);
+        ored_flags = ANYOF_FLAGS(or_with) & ANYOF_COMMON_FLAGS;
+    }
+
+    ANYOF_FLAGS(ssc) |= ored_flags;
+
+    /* Below, C1 is the list of code points in 'ssc'; P1, its posix classes.
+     * C2 is the list of code points in 'or-with'; P2, its posix classes.
+     * 'or_with' may be inverted.  When not inverted, we have the simple
+     * situation of computing:
+     *  (C1 | P1) | (C2 | P2)  =  (C1 | C2) | (P1 | P2)
+     * If P1|P2 yields a situation with both a class and its complement are
+     * set, like having both \w and \W, this matches all code points, and we
+     * can delete these from the P component of the ssc going forward.  XXX We
+     * might be able to delete all the P components, but I (khw) am not certain
+     * about this, and it is better to be safe.
+     *
+     * Inverted, we have
+     *  (C1 | P1) | ~(C2 | P2)  =  (C1 | P1) | (~C2 & ~P2)
+     *                         <=  (C1 | P1) | ~C2
+     *                         <=  (C1 | ~C2) | P1
+     * (which results in actually simpler code than the non-inverted case)
+     * */
+
+    if ((ANYOF_FLAGS(or_with) & ANYOF_INVERT)
+        && ! is_ANYOF_SYNTHETIC(or_with))
+    {
+        /* We ignore P2, leaving P1 going forward */
+    }   /* else  Not inverted */
+    else if (ANYOF_FLAGS(or_with) & ANYOF_POSIXL) {
+        ANYOF_POSIXL_OR((regnode_charclass_posixl*)or_with, ssc);
+        if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)) {
+            unsigned int i;
+            for (i = 0; i < ANYOF_MAX; i += 2) {
+                if (ANYOF_POSIXL_TEST(ssc, i) && ANYOF_POSIXL_TEST(ssc, i + 1))
+                {
+                    ssc_match_all_cp(ssc);
+                    ANYOF_POSIXL_CLEAR(ssc, i);
+                    ANYOF_POSIXL_CLEAR(ssc, i+1);
+                }
+            }
+        }
+    }
+
+    ssc_union(ssc,
+              ored_cp_list,
+              FALSE /* Already has been inverted */
+              );
+}
+
+PERL_STATIC_INLINE void
+S_ssc_union(pTHX_ regnode_ssc *ssc, SV* const invlist, const bool invert2nd)
+{
+    PERL_ARGS_ASSERT_SSC_UNION;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    _invlist_union_maybe_complement_2nd(ssc->invlist,
+                                        invlist,
+                                        invert2nd,
+                                        &ssc->invlist);
+}
+
+PERL_STATIC_INLINE void
+S_ssc_intersection(pTHX_ regnode_ssc *ssc,
+                         SV* const invlist,
+                         const bool invert2nd)
+{
+    PERL_ARGS_ASSERT_SSC_INTERSECTION;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    _invlist_intersection_maybe_complement_2nd(ssc->invlist,
+                                               invlist,
+                                               invert2nd,
+                                               &ssc->invlist);
+}
+
+PERL_STATIC_INLINE void
+S_ssc_add_range(pTHX_ regnode_ssc *ssc, const UV start, const UV end)
+{
+    PERL_ARGS_ASSERT_SSC_ADD_RANGE;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    ssc->invlist = _add_range_to_invlist(ssc->invlist, start, end);
+}
+
+PERL_STATIC_INLINE void
+S_ssc_cp_and(pTHX_ regnode_ssc *ssc, const UV cp)
+{
+    /* AND just the single code point 'cp' into the SSC 'ssc' */
+
+    SV* cp_list = _new_invlist(2);
+
+    PERL_ARGS_ASSERT_SSC_CP_AND;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    cp_list = add_cp_to_invlist(cp_list, cp);
+    ssc_intersection(ssc, cp_list,
+                     FALSE /* Not inverted */
+                     );
+    SvREFCNT_dec_NN(cp_list);
+}
+
+PERL_STATIC_INLINE void
+S_ssc_clear_locale(pTHX_ regnode_ssc *ssc)
+{
+    /* Set the SSC 'ssc' to not match any locale things */
+
+    PERL_ARGS_ASSERT_SSC_CLEAR_LOCALE;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    ANYOF_POSIXL_ZERO(ssc);
+    ANYOF_FLAGS(ssc) &= ~ANYOF_LOCALE_FLAGS;
+}
+
+STATIC void
+S_ssc_finalize(pTHX_ RExC_state_t *pRExC_state, regnode_ssc *ssc)
+{
+    /* The inversion list in the SSC is marked mortal; now we need a more
+     * permanent copy, which is stored the same way that is done in a regular
+     * ANYOF node, with the first 256 code points in a bit map */
+
+    SV* invlist = invlist_clone(ssc->invlist);
+
+    PERL_ARGS_ASSERT_SSC_FINALIZE;
+
+    assert(is_ANYOF_SYNTHETIC(ssc));
+
+    /* The code in this file assumes that all but these flags aren't relevant
+     * to the SSC, except ANYOF_EMPTY_STRING, which should be cleared by the
+     * time we reach here */
+    assert(! (ANYOF_FLAGS(ssc) & ~ANYOF_COMMON_FLAGS));
+
+    populate_ANYOF_from_invlist( (regnode *) ssc, &invlist);
+
+    set_ANYOF_arg(pRExC_state, (regnode *) ssc, invlist,
+                                NULL, NULL, NULL, FALSE);
+
+    /* Make sure is clone-safe */
+    ssc->invlist = NULL;
+
+    if (ANYOF_POSIXL_SSC_TEST_ANY_SET(ssc)) {
+        ANYOF_FLAGS(ssc) |= ANYOF_POSIXL;
+    }
+
+    assert(! (ANYOF_FLAGS(ssc) & ANYOF_LOCALE_FLAGS) || RExC_contains_locale);
+}
+
+#define TRIE_LIST_ITEM(state,idx) (trie->states[state].trans.list)[ idx ]
+#define TRIE_LIST_CUR(state)  ( TRIE_LIST_ITEM( state, 0 ).forid )
+#define TRIE_LIST_LEN(state) ( TRIE_LIST_ITEM( state, 0 ).newstate )
+#define TRIE_LIST_USED(idx)  ( trie->states[state].trans.list         \
+                               ? (TRIE_LIST_CUR( idx ) - 1)           \
+                               : 0 )
+
+
+#ifdef DEBUGGING
+/*
+   dump_trie(trie,widecharmap,revcharmap)
+   dump_trie_interim_list(trie,widecharmap,revcharmap,next_alloc)
+   dump_trie_interim_table(trie,widecharmap,revcharmap,next_alloc)
+
+   These routines dump out a trie in a somewhat readable format.
+   The _interim_ variants are used for debugging the interim
+   tables that are used to generate the final compressed
+   representation which is what dump_trie expects.
+
+   Part of the reason for their existence is to provide a form
+   of documentation as to how the different representations function.
+
+*/
+
+/*
+  Dumps the final compressed table form of the trie to Perl_debug_log.
+  Used for debugging make_trie().
+*/
+
+STATIC void
+S_dump_trie(pTHX_ const struct _reg_trie_data *trie, HV *widecharmap,
+           AV *revcharmap, U32 depth)
+{
+    U32 state;
+    SV *sv=sv_newmortal();
+    int colwidth= widecharmap ? 6 : 4;
+    U16 word;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_DUMP_TRIE;
+
+    PerlIO_printf( Perl_debug_log, "%*sChar : %-6s%-6s%-4s ",
+        (int)depth * 2 + 2,"",
+        "Match","Base","Ofs" );
+
+    for( state = 0 ; state < trie->uniquecharcount ; state++ ) {
+       SV ** const tmp = av_fetch( revcharmap, state, 0);
+        if ( tmp ) {
+            PerlIO_printf( Perl_debug_log, "%*s",
+                colwidth,
+                pv_pretty(sv, SvPV_nolen_const(*tmp), SvCUR(*tmp), colwidth,
+                           PL_colors[0], PL_colors[1],
+                           (SvUTF8(*tmp) ? PERL_PV_ESCAPE_UNI : 0) |
+                           PERL_PV_ESCAPE_FIRSTCHAR
+                )
+            );
+        }
+    }
+    PerlIO_printf( Perl_debug_log, "\n%*sState|-----------------------",
+        (int)depth * 2 + 2,"");
+
+    for( state = 0 ; state < trie->uniquecharcount ; state++ )
+        PerlIO_printf( Perl_debug_log, "%.*s", colwidth, "--------");
+    PerlIO_printf( Perl_debug_log, "\n");
+
+    for( state = 1 ; state < trie->statecount ; state++ ) {
+       const U32 base = trie->states[ state ].trans.base;
+
+        PerlIO_printf( Perl_debug_log, "%*s#%4"UVXf"|",
+                                       (int)depth * 2 + 2,"", (UV)state);
+
+        if ( trie->states[ state ].wordnum ) {
+            PerlIO_printf( Perl_debug_log, " W%4X",
+                                           trie->states[ state ].wordnum );
+        } else {
+            PerlIO_printf( Perl_debug_log, "%6s", "" );
+        }
+
+        PerlIO_printf( Perl_debug_log, " @%4"UVXf" ", (UV)base );
+
+        if ( base ) {
+            U32 ofs = 0;
+
+            while( ( base + ofs  < trie->uniquecharcount ) ||
+                   ( base + ofs - trie->uniquecharcount < trie->lasttrans
+                     && trie->trans[ base + ofs - trie->uniquecharcount ].check
+                                                                    != state))
+                    ofs++;
+
+            PerlIO_printf( Perl_debug_log, "+%2"UVXf"[ ", (UV)ofs);
+
+            for ( ofs = 0 ; ofs < trie->uniquecharcount ; ofs++ ) {
+                if ( ( base + ofs >= trie->uniquecharcount )
+                        && ( base + ofs - trie->uniquecharcount
+                                                        < trie->lasttrans )
+                        && trie->trans[ base + ofs
+                                    - trie->uniquecharcount ].check == state )
+                {
+                   PerlIO_printf( Perl_debug_log, "%*"UVXf,
+                    colwidth,
+                    (UV)trie->trans[ base + ofs
+                                             - trie->uniquecharcount ].next );
+                } else {
+                    PerlIO_printf( Perl_debug_log, "%*s",colwidth,"   ." );
+                }
+            }
+
+            PerlIO_printf( Perl_debug_log, "]");
+
+        }
+        PerlIO_printf( Perl_debug_log, "\n" );
+    }
+    PerlIO_printf(Perl_debug_log, "%*sword_info N:(prev,len)=",
+                                (int)depth*2, "");
+    for (word=1; word <= trie->wordcount; word++) {
+       PerlIO_printf(Perl_debug_log, " %d:(%d,%d)",
+           (int)word, (int)(trie->wordinfo[word].prev),
+           (int)(trie->wordinfo[word].len));
+    }
+    PerlIO_printf(Perl_debug_log, "\n" );
+}
+/*
+  Dumps a fully constructed but uncompressed trie in list form.
+  List tries normally only are used for construction when the number of
+  possible chars (trie->uniquecharcount) is very high.
+  Used for debugging make_trie().
+*/
+STATIC void
+S_dump_trie_interim_list(pTHX_ const struct _reg_trie_data *trie,
+                        HV *widecharmap, AV *revcharmap, U32 next_alloc,
+                        U32 depth)
+{
+    U32 state;
+    SV *sv=sv_newmortal();
+    int colwidth= widecharmap ? 6 : 4;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_DUMP_TRIE_INTERIM_LIST;
+
+    /* print out the table precompression.  */
+    PerlIO_printf( Perl_debug_log, "%*sState :Word | Transition Data\n%*s%s",
+        (int)depth * 2 + 2,"", (int)depth * 2 + 2,"",
+        "------:-----+-----------------\n" );
+
+    for( state=1 ; state < next_alloc ; state ++ ) {
+        U16 charid;
+
+        PerlIO_printf( Perl_debug_log, "%*s %4"UVXf" :",
+            (int)depth * 2 + 2,"", (UV)state  );
+        if ( ! trie->states[ state ].wordnum ) {
+            PerlIO_printf( Perl_debug_log, "%5s| ","");
+        } else {
+            PerlIO_printf( Perl_debug_log, "W%4x| ",
+                trie->states[ state ].wordnum
+            );
+        }
+        for( charid = 1 ; charid <= TRIE_LIST_USED( state ) ; charid++ ) {
+           SV ** const tmp = av_fetch( revcharmap,
+                                        TRIE_LIST_ITEM(state,charid).forid, 0);
+           if ( tmp ) {
+                PerlIO_printf( Perl_debug_log, "%*s:%3X=%4"UVXf" | ",
+                    colwidth,
+                    pv_pretty(sv, SvPV_nolen_const(*tmp), SvCUR(*tmp),
+                              colwidth,
+                              PL_colors[0], PL_colors[1],
+                              (SvUTF8(*tmp) ? PERL_PV_ESCAPE_UNI : 0)
+                              | PERL_PV_ESCAPE_FIRSTCHAR
+                    ) ,
+                    TRIE_LIST_ITEM(state,charid).forid,
+                    (UV)TRIE_LIST_ITEM(state,charid).newstate
+                );
+                if (!(charid % 10))
+                    PerlIO_printf(Perl_debug_log, "\n%*s| ",
+                        (int)((depth * 2) + 14), "");
+            }
+        }
+        PerlIO_printf( Perl_debug_log, "\n");
+    }
+}
+
+/*
+  Dumps a fully constructed but uncompressed trie in table form.
+  This is the normal DFA style state transition table, with a few
+  twists to facilitate compression later.
+  Used for debugging make_trie().
+*/
+STATIC void
+S_dump_trie_interim_table(pTHX_ const struct _reg_trie_data *trie,
+                         HV *widecharmap, AV *revcharmap, U32 next_alloc,
+                         U32 depth)
+{
+    U32 state;
+    U16 charid;
+    SV *sv=sv_newmortal();
+    int colwidth= widecharmap ? 6 : 4;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_DUMP_TRIE_INTERIM_TABLE;
+
+    /*
+       print out the table precompression so that we can do a visual check
+       that they are identical.
+     */
+
+    PerlIO_printf( Perl_debug_log, "%*sChar : ",(int)depth * 2 + 2,"" );
+
+    for( charid = 0 ; charid < trie->uniquecharcount ; charid++ ) {
+       SV ** const tmp = av_fetch( revcharmap, charid, 0);
+        if ( tmp ) {
+            PerlIO_printf( Perl_debug_log, "%*s",
+                colwidth,
+                pv_pretty(sv, SvPV_nolen_const(*tmp), SvCUR(*tmp), colwidth,
+                           PL_colors[0], PL_colors[1],
+                           (SvUTF8(*tmp) ? PERL_PV_ESCAPE_UNI : 0) |
+                           PERL_PV_ESCAPE_FIRSTCHAR
+                )
+            );
+        }
+    }
+
+    PerlIO_printf( Perl_debug_log, "\n%*sState+-",(int)depth * 2 + 2,"" );
+
+    for( charid=0 ; charid < trie->uniquecharcount ; charid++ ) {
+        PerlIO_printf( Perl_debug_log, "%.*s", colwidth,"--------");
+    }
+
+    PerlIO_printf( Perl_debug_log, "\n" );
+
+    for( state=1 ; state < next_alloc ; state += trie->uniquecharcount ) {
+
+        PerlIO_printf( Perl_debug_log, "%*s%4"UVXf" : ",
+            (int)depth * 2 + 2,"",
+            (UV)TRIE_NODENUM( state ) );
+
+        for( charid = 0 ; charid < trie->uniquecharcount ; charid++ ) {
+            UV v=(UV)SAFE_TRIE_NODENUM( trie->trans[ state + charid ].next );
+            if (v)
+                PerlIO_printf( Perl_debug_log, "%*"UVXf, colwidth, v );
+            else
+                PerlIO_printf( Perl_debug_log, "%*s", colwidth, "." );
+        }
+        if ( ! trie->states[ TRIE_NODENUM( state ) ].wordnum ) {
+            PerlIO_printf( Perl_debug_log, " (%4"UVXf")\n",
+                                            (UV)trie->trans[ state ].check );
+        } else {
+            PerlIO_printf( Perl_debug_log, " (%4"UVXf") W%4X\n",
+                                            (UV)trie->trans[ state ].check,
+            trie->states[ TRIE_NODENUM( state ) ].wordnum );
+        }
+    }
+}
+
+#endif
+
+
+/* make_trie(startbranch,first,last,tail,word_count,flags,depth)
+  startbranch: the first branch in the whole branch sequence
+  first      : start branch of sequence of branch-exact nodes.
+              May be the same as startbranch
+  last       : Thing following the last branch.
+              May be the same as tail.
+  tail       : item following the branch sequence
+  count      : words in the sequence
+  flags      : currently the OP() type we will be building one of /EXACT(|F|Fl)/
+  depth      : indent depth
+
+Inplace optimizes a sequence of 2 or more Branch-Exact nodes into a TRIE node.
+
+A trie is an N'ary tree where the branches are determined by digital
+decomposition of the key. IE, at the root node you look up the 1st character and
+follow that branch repeat until you find the end of the branches. Nodes can be
+marked as "accepting" meaning they represent a complete word. Eg:
+
+  /he|she|his|hers/
+
+would convert into the following structure. Numbers represent states, letters
+following numbers represent valid transitions on the letter from that state, if
+the number is in square brackets it represents an accepting state, otherwise it
+will be in parenthesis.
+
+      +-h->+-e->[3]-+-r->(8)-+-s->[9]
+      |    |
+      |   (2)
+      |    |
+     (1)   +-i->(6)-+-s->[7]
+      |
+      +-s->(3)-+-h->(4)-+-e->[5]
+
+      Accept Word Mapping: 3=>1 (he),5=>2 (she), 7=>3 (his), 9=>4 (hers)
+
+This shows that when matching against the string 'hers' we will begin at state 1
+read 'h' and move to state 2, read 'e' and move to state 3 which is accepting,
+then read 'r' and go to state 8 followed by 's' which takes us to state 9 which
+is also accepting. Thus we know that we can match both 'he' and 'hers' with a
+single traverse. We store a mapping from accepting to state to which word was
+matched, and then when we have multiple possibilities we try to complete the
+rest of the regex in the order in which they occured in the alternation.
+
+The only prior NFA like behaviour that would be changed by the TRIE support is
+the silent ignoring of duplicate alternations which are of the form:
+
+ / (DUPE|DUPE) X? (?{ ... }) Y /x
+
+Thus EVAL blocks following a trie may be called a different number of times with
+and without the optimisation. With the optimisations dupes will be silently
+ignored. This inconsistent behaviour of EVAL type nodes is well established as
+the following demonstrates:
+
+ 'words'=~/(word|word|word)(?{ print $1 })[xyz]/
+
+which prints out 'word' three times, but
+
+ 'words'=~/(word|word|word)(?{ print $1 })S/
+
+which doesnt print it out at all. This is due to other optimisations kicking in.
+
+Example of what happens on a structural level:
+
+The regexp /(ac|ad|ab)+/ will produce the following debug output:
+
+   1: CURLYM[1] {1,32767}(18)
+   5:   BRANCH(8)
+   6:     EXACT <ac>(16)
+   8:   BRANCH(11)
+   9:     EXACT <ad>(16)
+  11:   BRANCH(14)
+  12:     EXACT <ab>(16)
+  16:   SUCCEED(0)
+  17:   NOTHING(18)
+  18: END(0)
+
+This would be optimizable with startbranch=5, first=5, last=16, tail=16
+and should turn into:
+
+   1: CURLYM[1] {1,32767}(18)
+   5:   TRIE(16)
+       [Words:3 Chars Stored:6 Unique Chars:4 States:5 NCP:1]
+         <ac>
+         <ad>
+         <ab>
+  16:   SUCCEED(0)
+  17:   NOTHING(18)
+  18: END(0)
+
+Cases where tail != last would be like /(?foo|bar)baz/:
+
+   1: BRANCH(4)
+   2:   EXACT <foo>(8)
+   4: BRANCH(7)
+   5:   EXACT <bar>(8)
+   7: TAIL(8)
+   8: EXACT <baz>(10)
+  10: END(0)
+
+which would be optimizable with startbranch=1, first=1, last=7, tail=8
+and would end up looking like:
+
+    1: TRIE(8)
+      [Words:2 Chars Stored:6 Unique Chars:5 States:7 NCP:1]
+       <foo>
+       <bar>
+   7: TAIL(8)
+   8: EXACT <baz>(10)
+  10: END(0)
+
+    d = uvchr_to_utf8_flags(d, uv, 0);
+
+is the recommended Unicode-aware way of saying
+
+    *(d++) = uv;
+*/
+
+#define TRIE_STORE_REVCHAR(val)                                            \
+    STMT_START {                                                           \
+       if (UTF) {                                                         \
+            SV *zlopp = newSV(7); /* XXX: optimize me */                   \
+           unsigned char *flrbbbbb = (unsigned char *) SvPVX(zlopp);      \
+            unsigned const char *const kapow = uvchr_to_utf8(flrbbbbb, val); \
+           SvCUR_set(zlopp, kapow - flrbbbbb);                            \
+           SvPOK_on(zlopp);                                               \
+           SvUTF8_on(zlopp);                                              \
+           av_push(revcharmap, zlopp);                                    \
+       } else {                                                           \
+            char ooooff = (char)val;                                           \
+           av_push(revcharmap, newSVpvn(&ooooff, 1));                     \
+       }                                                                  \
+        } STMT_END
+
+/* This gets the next character from the input, folding it if not already
+ * folded. */
+#define TRIE_READ_CHAR STMT_START {                                           \
+    wordlen++;                                                                \
+    if ( UTF ) {                                                              \
+        /* if it is UTF then it is either already folded, or does not need    \
+         * folding */                                                         \
+        uvc = valid_utf8_to_uvchr( (const U8*) uc, &len);                     \
+    }                                                                         \
+    else if (folder == PL_fold_latin1) {                                      \
+        /* This folder implies Unicode rules, which in the range expressible  \
+         *  by not UTF is the lower case, with the two exceptions, one of     \
+         *  which should have been taken care of before calling this */       \
+        assert(*uc != LATIN_SMALL_LETTER_SHARP_S);                            \
+        uvc = toLOWER_L1(*uc);                                                \
+        if (UNLIKELY(uvc == MICRO_SIGN)) uvc = GREEK_SMALL_LETTER_MU;         \
+        len = 1;                                                              \
+    } else {                                                                  \
+        /* raw data, will be folded later if needed */                        \
+        uvc = (U32)*uc;                                                       \
+        len = 1;                                                              \
+    }                                                                         \
+} STMT_END
+
+
+
+#define TRIE_LIST_PUSH(state,fid,ns) STMT_START {               \
+    if ( TRIE_LIST_CUR( state ) >=TRIE_LIST_LEN( state ) ) {    \
+       U32 ging = TRIE_LIST_LEN( state ) *= 2;                 \
+       Renew( trie->states[ state ].trans.list, ging, reg_trie_trans_le ); \
+    }                                                           \
+    TRIE_LIST_ITEM( state, TRIE_LIST_CUR( state ) ).forid = fid;     \
+    TRIE_LIST_ITEM( state, TRIE_LIST_CUR( state ) ).newstate = ns;   \
+    TRIE_LIST_CUR( state )++;                                   \
+} STMT_END
+
+#define TRIE_LIST_NEW(state) STMT_START {                       \
+    Newxz( trie->states[ state ].trans.list,               \
+       4, reg_trie_trans_le );                                 \
+     TRIE_LIST_CUR( state ) = 1;                                \
+     TRIE_LIST_LEN( state ) = 4;                                \
+} STMT_END
+
+#define TRIE_HANDLE_WORD(state) STMT_START {                    \
+    U16 dupe= trie->states[ state ].wordnum;                    \
+    regnode * const noper_next = regnext( noper );              \
+                                                                \
+    DEBUG_r({                                                   \
+        /* store the word for dumping */                        \
+        SV* tmp;                                                \
+        if (OP(noper) != NOTHING)                               \
+            tmp = newSVpvn_utf8(STRING(noper), STR_LEN(noper), UTF);   \
+        else                                                    \
+            tmp = newSVpvn_utf8( "", 0, UTF );                 \
+        av_push( trie_words, tmp );                             \
+    });                                                         \
+                                                                \
+    curword++;                                                  \
+    trie->wordinfo[curword].prev   = 0;                         \
+    trie->wordinfo[curword].len    = wordlen;                   \
+    trie->wordinfo[curword].accept = state;                     \
+                                                                \
+    if ( noper_next < tail ) {                                  \
+        if (!trie->jump)                                        \
+            trie->jump = (U16 *) PerlMemShared_calloc( word_count + 1, \
+                                                 sizeof(U16) ); \
+        trie->jump[curword] = (U16)(noper_next - convert);      \
+        if (!jumper)                                            \
+            jumper = noper_next;                                \
+        if (!nextbranch)                                        \
+            nextbranch= regnext(cur);                           \
+    }                                                           \
+                                                                \
+    if ( dupe ) {                                               \
+        /* It's a dupe. Pre-insert into the wordinfo[].prev   */\
+        /* chain, so that when the bits of chain are later    */\
+        /* linked together, the dups appear in the chain      */\
+       trie->wordinfo[curword].prev = trie->wordinfo[dupe].prev; \
+       trie->wordinfo[dupe].prev = curword;                    \
+    } else {                                                    \
+        /* we haven't inserted this word yet.                */ \
+        trie->states[ state ].wordnum = curword;                \
+    }                                                           \
+} STMT_END
+
+
+#define TRIE_TRANS_STATE(state,base,ucharcount,charid,special)         \
+     ( ( base + charid >=  ucharcount                                  \
+         && base + charid < ubound                                     \
+         && state == trie->trans[ base - ucharcount + charid ].check   \
+         && trie->trans[ base - ucharcount + charid ].next )           \
+           ? trie->trans[ base - ucharcount + charid ].next            \
+           : ( state==1 ? special : 0 )                                        \
+      )
+
+#define MADE_TRIE       1
+#define MADE_JUMP_TRIE  2
+#define MADE_EXACT_TRIE 4
+
+STATIC I32
+S_make_trie(pTHX_ RExC_state_t *pRExC_state, regnode *startbranch,
+                  regnode *first, regnode *last, regnode *tail,
+                  U32 word_count, U32 flags, U32 depth)
+{
+    dVAR;
+    /* first pass, loop through and scan words */
+    reg_trie_data *trie;
+    HV *widecharmap = NULL;
+    AV *revcharmap = newAV();
+    regnode *cur;
+    STRLEN len = 0;
+    UV uvc = 0;
+    U16 curword = 0;
+    U32 next_alloc = 0;
+    regnode *jumper = NULL;
+    regnode *nextbranch = NULL;
+    regnode *convert = NULL;
+    U32 *prev_states; /* temp array mapping each state to previous one */
+    /* we just use folder as a flag in utf8 */
+    const U8 * folder = NULL;
+
+#ifdef DEBUGGING
+    const U32 data_slot = add_data( pRExC_state, STR_WITH_LEN("tuuu"));
+    AV *trie_words = NULL;
+    /* along with revcharmap, this only used during construction but both are
+     * useful during debugging so we store them in the struct when debugging.
+     */
+#else
+    const U32 data_slot = add_data( pRExC_state, STR_WITH_LEN("tu"));
+    STRLEN trie_charcount=0;
+#endif
+    SV *re_trie_maxbuff;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_MAKE_TRIE;
+#ifndef DEBUGGING
+    PERL_UNUSED_ARG(depth);
+#endif
+
+    switch (flags) {
+        case EXACT: break;
+       case EXACTFA:
+        case EXACTFU_SS:
+       case EXACTFU: folder = PL_fold_latin1; break;
+       case EXACTF:  folder = PL_fold; break;
+        default: Perl_croak( aTHX_ "panic! In trie construction, unknown node type %u %s", (unsigned) flags, PL_reg_name[flags] );
+    }
+
+    trie = (reg_trie_data *) PerlMemShared_calloc( 1, sizeof(reg_trie_data) );
+    trie->refcount = 1;
+    trie->startstate = 1;
+    trie->wordcount = word_count;
+    RExC_rxi->data->data[ data_slot ] = (void*)trie;
+    trie->charmap = (U16 *) PerlMemShared_calloc( 256, sizeof(U16) );
+    if (flags == EXACT)
+       trie->bitmap = (char *) PerlMemShared_calloc( ANYOF_BITMAP_SIZE, 1 );
+    trie->wordinfo = (reg_trie_wordinfo *) PerlMemShared_calloc(
+                       trie->wordcount+1, sizeof(reg_trie_wordinfo));
+
+    DEBUG_r({
+        trie_words = newAV();
+    });
+
+    re_trie_maxbuff = get_sv(RE_TRIE_MAXBUF_NAME, 1);
+    if (!SvIOK(re_trie_maxbuff)) {
+        sv_setiv(re_trie_maxbuff, RE_TRIE_MAXBUF_INIT);
+    }
+    DEBUG_TRIE_COMPILE_r({
+        PerlIO_printf( Perl_debug_log,
+          "%*smake_trie start==%d, first==%d, last==%d, tail==%d depth=%d\n",
+          (int)depth * 2 + 2, "",
+          REG_NODE_NUM(startbranch),REG_NODE_NUM(first),
+          REG_NODE_NUM(last), REG_NODE_NUM(tail), (int)depth);
+    });
+
+   /* Find the node we are going to overwrite */
+    if ( first == startbranch && OP( last ) != BRANCH ) {
+        /* whole branch chain */
+        convert = first;
+    } else {
+        /* branch sub-chain */
+        convert = NEXTOPER( first );
+    }
+
+    /*  -- First loop and Setup --
+
+       We first traverse the branches and scan each word to determine if it
+       contains widechars, and how many unique chars there are, this is
+       important as we have to build a table with at least as many columns as we
+       have unique chars.
+
+       We use an array of integers to represent the character codes 0..255
+       (trie->charmap) and we use a an HV* to store Unicode characters. We use
+       the native representation of the character value as the key and IV's for
+       the coded index.
+
+       *TODO* If we keep track of how many times each character is used we can
+       remap the columns so that the table compression later on is more
+       efficient in terms of memory by ensuring the most common value is in the
+       middle and the least common are on the outside.  IMO this would be better
+       than a most to least common mapping as theres a decent chance the most
+       common letter will share a node with the least common, meaning the node
+       will not be compressible. With a middle is most common approach the worst
+       case is when we have the least common nodes twice.
+
+     */
+
+    for ( cur = first ; cur < last ; cur = regnext( cur ) ) {
+        regnode *noper = NEXTOPER( cur );
+        const U8 *uc = (U8*)STRING( noper );
+        const U8 *e  = uc + STR_LEN( noper );
+        int foldlen = 0;
+        U32 wordlen      = 0;         /* required init */
+        STRLEN minchars = 0;
+        STRLEN maxchars = 0;
+        bool set_bit = trie->bitmap ? 1 : 0; /*store the first char in the
+                                               bitmap?*/
+
+        if (OP(noper) == NOTHING) {
+            regnode *noper_next= regnext(noper);
+            if (noper_next != tail && OP(noper_next) == flags) {
+                noper = noper_next;
+                uc= (U8*)STRING(noper);
+                e= uc + STR_LEN(noper);
+               trie->minlen= STR_LEN(noper);
+            } else {
+               trie->minlen= 0;
+               continue;
+           }
+        }
+
+        if ( set_bit ) { /* bitmap only alloced when !(UTF&&Folding) */
+            TRIE_BITMAP_SET(trie,*uc); /* store the raw first byte
+                                          regardless of encoding */
+            if (OP( noper ) == EXACTFU_SS) {
+                /* false positives are ok, so just set this */
+                TRIE_BITMAP_SET(trie, LATIN_SMALL_LETTER_SHARP_S);
+            }
+        }
+        for ( ; uc < e ; uc += len ) {  /* Look at each char in the current
+                                           branch */
+            TRIE_CHARCOUNT(trie)++;
+            TRIE_READ_CHAR;
+
+            /* TRIE_READ_CHAR returns the current character, or its fold if /i
+             * is in effect.  Under /i, this character can match itself, or
+             * anything that folds to it.  If not under /i, it can match just
+             * itself.  Most folds are 1-1, for example k, K, and KELVIN SIGN
+             * all fold to k, and all are single characters.   But some folds
+             * expand to more than one character, so for example LATIN SMALL
+             * LIGATURE FFI folds to the three character sequence 'ffi'.  If
+             * the string beginning at 'uc' is 'ffi', it could be matched by
+             * three characters, or just by the one ligature character. (It
+             * could also be matched by two characters: LATIN SMALL LIGATURE FF
+             * followed by 'i', or by 'f' followed by LATIN SMALL LIGATURE FI).
+             * (Of course 'I' and/or 'F' instead of 'i' and 'f' can also
+             * match.)  The trie needs to know the minimum and maximum number
+             * of characters that could match so that it can use size alone to
+             * quickly reject many match attempts.  The max is simple: it is
+             * the number of folded characters in this branch (since a fold is
+             * never shorter than what folds to it. */
+
+            maxchars++;
+
+            /* And the min is equal to the max if not under /i (indicated by
+             * 'folder' being NULL), or there are no multi-character folds.  If
+             * there is a multi-character fold, the min is incremented just
+             * once, for the character that folds to the sequence.  Each
+             * character in the sequence needs to be added to the list below of
+             * characters in the trie, but we count only the first towards the
+             * min number of characters needed.  This is done through the
+             * variable 'foldlen', which is returned by the macros that look
+             * for these sequences as the number of bytes the sequence
+             * occupies.  Each time through the loop, we decrement 'foldlen' by
+             * how many bytes the current char occupies.  Only when it reaches
+             * 0 do we increment 'minchars' or look for another multi-character
+             * sequence. */
+            if (folder == NULL) {
+                minchars++;
+            }
+            else if (foldlen > 0) {
+                foldlen -= (UTF) ? UTF8SKIP(uc) : 1;
+            }
+            else {
+                minchars++;
+
+                /* See if *uc is the beginning of a multi-character fold.  If
+                 * so, we decrement the length remaining to look at, to account
+                 * for the current character this iteration.  (We can use 'uc'
+                 * instead of the fold returned by TRIE_READ_CHAR because for
+                 * non-UTF, the latin1_safe macro is smart enough to account
+                 * for all the unfolded characters, and because for UTF, the
+                 * string will already have been folded earlier in the
+                 * compilation process */
+                if (UTF) {
+                    if ((foldlen = is_MULTI_CHAR_FOLD_utf8_safe(uc, e))) {
+                        foldlen -= UTF8SKIP(uc);
+                    }
+                }
+                else if ((foldlen = is_MULTI_CHAR_FOLD_latin1_safe(uc, e))) {
+                    foldlen--;
+                }
+            }
+
+            /* The current character (and any potential folds) should be added
+             * to the possible matching characters for this position in this
+             * branch */
+            if ( uvc < 256 ) {
+                if ( folder ) {
+                    U8 folded= folder[ (U8) uvc ];
+                    if ( !trie->charmap[ folded ] ) {
+                        trie->charmap[ folded ]=( ++trie->uniquecharcount );
+                        TRIE_STORE_REVCHAR( folded );
+                    }
+                }
+                if ( !trie->charmap[ uvc ] ) {
+                    trie->charmap[ uvc ]=( ++trie->uniquecharcount );
+                    TRIE_STORE_REVCHAR( uvc );
+                }
+                if ( set_bit ) {
+                   /* store the codepoint in the bitmap, and its folded
+                    * equivalent. */
+                    TRIE_BITMAP_SET(trie, uvc);
+
+                   /* store the folded codepoint */
+                    if ( folder ) TRIE_BITMAP_SET(trie, folder[(U8) uvc ]);
+
+                   if ( !UTF ) {
+                       /* store first byte of utf8 representation of
+                          variant codepoints */
+                       if (! UVCHR_IS_INVARIANT(uvc)) {
+                           TRIE_BITMAP_SET(trie, UTF8_TWO_BYTE_HI(uvc));
+                       }
+                   }
+                    set_bit = 0; /* We've done our bit :-) */
+                }
+            } else {
+
+                /* XXX We could come up with the list of code points that fold
+                 * to this using PL_utf8_foldclosures, except not for
+                 * multi-char folds, as there may be multiple combinations
+                 * there that could work, which needs to wait until runtime to
+                 * resolve (The comment about LIGATURE FFI above is such an
+                 * example */
+
+                SV** svpp;
+                if ( !widecharmap )
+                    widecharmap = newHV();
+
+                svpp = hv_fetch( widecharmap, (char*)&uvc, sizeof( UV ), 1 );
+
+                if ( !svpp )
+                    Perl_croak( aTHX_ "error creating/fetching widecharmap entry for 0x%"UVXf, uvc );
+
+                if ( !SvTRUE( *svpp ) ) {
+                    sv_setiv( *svpp, ++trie->uniquecharcount );
+                    TRIE_STORE_REVCHAR(uvc);
+                }
+            }
+        } /* end loop through characters in this branch of the trie */
+
+        /* We take the min and max for this branch and combine to find the min
+         * and max for all branches processed so far */
+        if( cur == first ) {
+            trie->minlen = minchars;
+            trie->maxlen = maxchars;
+        } else if (minchars < trie->minlen) {
+            trie->minlen = minchars;
+        } else if (maxchars > trie->maxlen) {
+            trie->maxlen = maxchars;
+        }
+    } /* end first pass */
+    DEBUG_TRIE_COMPILE_r(
+        PerlIO_printf( Perl_debug_log,
+                "%*sTRIE(%s): W:%d C:%d Uq:%d Min:%d Max:%d\n",
+                (int)depth * 2 + 2,"",
+                ( widecharmap ? "UTF8" : "NATIVE" ), (int)word_count,
+               (int)TRIE_CHARCOUNT(trie), trie->uniquecharcount,
+               (int)trie->minlen, (int)trie->maxlen )
+    );
+
+    /*
+        We now know what we are dealing with in terms of unique chars and
+        string sizes so we can calculate how much memory a naive
+        representation using a flat table  will take. If it's over a reasonable
+        limit (as specified by ${^RE_TRIE_MAXBUF}) we use a more memory
+        conservative but potentially much slower representation using an array
+        of lists.
+
+        At the end we convert both representations into the same compressed
+        form that will be used in regexec.c for matching with. The latter
+        is a form that cannot be used to construct with but has memory
+        properties similar to the list form and access properties similar
+        to the table form making it both suitable for fast searches and
+        small enough that its feasable to store for the duration of a program.
+
+        See the comment in the code where the compressed table is produced
+        inplace from the flat tabe representation for an explanation of how
+        the compression works.
+
+    */
+
+
+    Newx(prev_states, TRIE_CHARCOUNT(trie) + 2, U32);
+    prev_states[1] = 0;
+
+    if ( (IV)( ( TRIE_CHARCOUNT(trie) + 1 ) * trie->uniquecharcount + 1)
+                                                    > SvIV(re_trie_maxbuff) )
+    {
+        /*
+            Second Pass -- Array Of Lists Representation
+
+            Each state will be represented by a list of charid:state records
+            (reg_trie_trans_le) the first such element holds the CUR and LEN
+            points of the allocated array. (See defines above).
+
+            We build the initial structure using the lists, and then convert
+            it into the compressed table form which allows faster lookups
+            (but cant be modified once converted).
+        */
+
+        STRLEN transcount = 1;
+
+        DEBUG_TRIE_COMPILE_MORE_r( PerlIO_printf( Perl_debug_log,
+            "%*sCompiling trie using list compiler\n",
+            (int)depth * 2 + 2, ""));
+
+       trie->states = (reg_trie_state *)
+           PerlMemShared_calloc( TRIE_CHARCOUNT(trie) + 2,
+                                 sizeof(reg_trie_state) );
+        TRIE_LIST_NEW(1);
+        next_alloc = 2;
+
+        for ( cur = first ; cur < last ; cur = regnext( cur ) ) {
+
+            regnode *noper   = NEXTOPER( cur );
+           U8 *uc           = (U8*)STRING( noper );
+            const U8 *e      = uc + STR_LEN( noper );
+           U32 state        = 1;         /* required init */
+           U16 charid       = 0;         /* sanity init */
+            U32 wordlen      = 0;         /* required init */
+
+            if (OP(noper) == NOTHING) {
+                regnode *noper_next= regnext(noper);
+                if (noper_next != tail && OP(noper_next) == flags) {
+                    noper = noper_next;
+                    uc= (U8*)STRING(noper);
+                    e= uc + STR_LEN(noper);
+                }
+            }
+
+            if (OP(noper) != NOTHING) {
+                for ( ; uc < e ; uc += len ) {
+
+                    TRIE_READ_CHAR;
+
+                    if ( uvc < 256 ) {
+                        charid = trie->charmap[ uvc ];
+                   } else {
+                        SV** const svpp = hv_fetch( widecharmap,
+                                                    (char*)&uvc,
+                                                    sizeof( UV ),
+                                                    0);
+                        if ( !svpp ) {
+                            charid = 0;
+                        } else {
+                            charid=(U16)SvIV( *svpp );
+                        }
+                   }
+                    /* charid is now 0 if we dont know the char read, or
+                     * nonzero if we do */
+                    if ( charid ) {
+
+                        U16 check;
+                        U32 newstate = 0;
+
+                        charid--;
+                        if ( !trie->states[ state ].trans.list ) {
+                            TRIE_LIST_NEW( state );
+                       }
+                        for ( check = 1;
+                              check <= TRIE_LIST_USED( state );
+                              check++ )
+                        {
+                            if ( TRIE_LIST_ITEM( state, check ).forid
+                                                                    == charid )
+                            {
+                                newstate = TRIE_LIST_ITEM( state, check ).newstate;
+                                break;
+                            }
+                        }
+                        if ( ! newstate ) {
+                            newstate = next_alloc++;
+                           prev_states[newstate] = state;
+                            TRIE_LIST_PUSH( state, charid, newstate );
+                            transcount++;
+                        }
+                        state = newstate;
+                    } else {
+                        Perl_croak( aTHX_ "panic! In trie construction, no char mapping for %"IVdf, uvc );
+                   }
+               }
+           }
+            TRIE_HANDLE_WORD(state);
+
+        } /* end second pass */
+
+        /* next alloc is the NEXT state to be allocated */
+        trie->statecount = next_alloc;
+        trie->states = (reg_trie_state *)
+           PerlMemShared_realloc( trie->states,
+                                  next_alloc
+                                  * sizeof(reg_trie_state) );
+
+        /* and now dump it out before we compress it */
+        DEBUG_TRIE_COMPILE_MORE_r(dump_trie_interim_list(trie, widecharmap,
+                                                        revcharmap, next_alloc,
+                                                        depth+1)
+        );
+
+        trie->trans = (reg_trie_trans *)
+           PerlMemShared_calloc( transcount, sizeof(reg_trie_trans) );
+        {
+            U32 state;
+            U32 tp = 0;
+            U32 zp = 0;
+
+
+            for( state=1 ; state < next_alloc ; state ++ ) {
+                U32 base=0;
+
+                /*
+                DEBUG_TRIE_COMPILE_MORE_r(
+                    PerlIO_printf( Perl_debug_log, "tp: %d zp: %d ",tp,zp)
+                );
+                */
+
+                if (trie->states[state].trans.list) {
+                    U16 minid=TRIE_LIST_ITEM( state, 1).forid;
+                    U16 maxid=minid;
+                   U16 idx;
+
+                    for( idx = 2 ; idx <= TRIE_LIST_USED( state ) ; idx++ ) {
+                       const U16 forid = TRIE_LIST_ITEM( state, idx).forid;
+                       if ( forid < minid ) {
+                           minid=forid;
+                       } else if ( forid > maxid ) {
+                           maxid=forid;
+                       }
+                    }
+                    if ( transcount < tp + maxid - minid + 1) {
+                        transcount *= 2;
+                       trie->trans = (reg_trie_trans *)
+                           PerlMemShared_realloc( trie->trans,
+                                                    transcount
+                                                    * sizeof(reg_trie_trans) );
+                        Zero( trie->trans + (transcount / 2),
+                              transcount / 2,
+                              reg_trie_trans );
+                    }
+                    base = trie->uniquecharcount + tp - minid;
+                    if ( maxid == minid ) {
+                        U32 set = 0;
+                        for ( ; zp < tp ; zp++ ) {
+                            if ( ! trie->trans[ zp ].next ) {
+                                base = trie->uniquecharcount + zp - minid;
+                                trie->trans[ zp ].next = TRIE_LIST_ITEM( state,
+                                                                   1).newstate;
+                                trie->trans[ zp ].check = state;
+                                set = 1;
+                                break;
+                            }
+                        }
+                        if ( !set ) {
+                            trie->trans[ tp ].next = TRIE_LIST_ITEM( state,
+                                                                   1).newstate;
+                            trie->trans[ tp ].check = state;
+                            tp++;
+                            zp = tp;
+                        }
+                    } else {
+                        for ( idx=1; idx <= TRIE_LIST_USED( state ) ; idx++ ) {
+                            const U32 tid = base
+                                           - trie->uniquecharcount
+                                           + TRIE_LIST_ITEM( state, idx ).forid;
+                            trie->trans[ tid ].next = TRIE_LIST_ITEM( state,
+                                                                idx ).newstate;
+                            trie->trans[ tid ].check = state;
+                        }
+                        tp += ( maxid - minid + 1 );
+                    }
+                    Safefree(trie->states[ state ].trans.list);
+                }
+                /*
+                DEBUG_TRIE_COMPILE_MORE_r(
+                    PerlIO_printf( Perl_debug_log, " base: %d\n",base);
+                );
+                */
+                trie->states[ state ].trans.base=base;
+            }
+            trie->lasttrans = tp + 1;
+        }
+    } else {
+        /*
+           Second Pass -- Flat Table Representation.
+
+           we dont use the 0 slot of either trans[] or states[] so we add 1 to
+           each.  We know that we will need Charcount+1 trans at most to store
+           the data (one row per char at worst case) So we preallocate both
+           structures assuming worst case.
+
+           We then construct the trie using only the .next slots of the entry
+           structs.
+
+           We use the .check field of the first entry of the node temporarily
+           to make compression both faster and easier by keeping track of how
+           many non zero fields are in the node.
+
+           Since trans are numbered from 1 any 0 pointer in the table is a FAIL
+           transition.
+
+           There are two terms at use here: state as a TRIE_NODEIDX() which is
+           a number representing the first entry of the node, and state as a
+           TRIE_NODENUM() which is the trans number. state 1 is TRIE_NODEIDX(1)
+           and TRIE_NODENUM(1), state 2 is TRIE_NODEIDX(2) and TRIE_NODENUM(3)
+           if there are 2 entrys per node. eg:
+
+             A B       A B
+          1. 2 4    1. 3 7
+          2. 0 3    3. 0 5
+          3. 0 0    5. 0 0
+          4. 0 0    7. 0 0
+
+           The table is internally in the right hand, idx form. However as we
+           also have to deal with the states array which is indexed by nodenum
+           we have to use TRIE_NODENUM() to convert.
+
+        */
+        DEBUG_TRIE_COMPILE_MORE_r( PerlIO_printf( Perl_debug_log,
+            "%*sCompiling trie using table compiler\n",
+            (int)depth * 2 + 2, ""));
+
+       trie->trans = (reg_trie_trans *)
+           PerlMemShared_calloc( ( TRIE_CHARCOUNT(trie) + 1 )
+                                 * trie->uniquecharcount + 1,
+                                 sizeof(reg_trie_trans) );
+        trie->states = (reg_trie_state *)
+           PerlMemShared_calloc( TRIE_CHARCOUNT(trie) + 2,
+                                 sizeof(reg_trie_state) );
+        next_alloc = trie->uniquecharcount + 1;
+
+
+        for ( cur = first ; cur < last ; cur = regnext( cur ) ) {
+
+            regnode *noper   = NEXTOPER( cur );
+           const U8 *uc     = (U8*)STRING( noper );
+            const U8 *e      = uc + STR_LEN( noper );
+
+            U32 state        = 1;         /* required init */
+
+            U16 charid       = 0;         /* sanity init */
+            U32 accept_state = 0;         /* sanity init */
+
+            U32 wordlen      = 0;         /* required init */
+
+            if (OP(noper) == NOTHING) {
+                regnode *noper_next= regnext(noper);
+                if (noper_next != tail && OP(noper_next) == flags) {
+                    noper = noper_next;
+                    uc= (U8*)STRING(noper);
+                    e= uc + STR_LEN(noper);
+                }
+            }
+
+            if ( OP(noper) != NOTHING ) {
+                for ( ; uc < e ; uc += len ) {
+
+                    TRIE_READ_CHAR;
+
+                    if ( uvc < 256 ) {
+                        charid = trie->charmap[ uvc ];
+                    } else {
+                        SV* const * const svpp = hv_fetch( widecharmap,
+                                                           (char*)&uvc,
+                                                           sizeof( UV ),
+                                                           0);
+                        charid = svpp ? (U16)SvIV(*svpp) : 0;
+                    }
+                    if ( charid ) {
+                        charid--;
+                        if ( !trie->trans[ state + charid ].next ) {
+                            trie->trans[ state + charid ].next = next_alloc;
+                            trie->trans[ state ].check++;
+                           prev_states[TRIE_NODENUM(next_alloc)]
+                                   = TRIE_NODENUM(state);
+                            next_alloc += trie->uniquecharcount;
+                        }
+                        state = trie->trans[ state + charid ].next;
+                    } else {
+                        Perl_croak( aTHX_ "panic! In trie construction, no char mapping for %"IVdf, uvc );
+                    }
+                    /* charid is now 0 if we dont know the char read, or
+                     * nonzero if we do */
+                }
+            }
+            accept_state = TRIE_NODENUM( state );
+            TRIE_HANDLE_WORD(accept_state);
+
+        } /* end second pass */
+
+        /* and now dump it out before we compress it */
+        DEBUG_TRIE_COMPILE_MORE_r(dump_trie_interim_table(trie, widecharmap,
+                                                         revcharmap,
+                                                         next_alloc, depth+1));
+
+        {
+        /*
+           * Inplace compress the table.*
+
+           For sparse data sets the table constructed by the trie algorithm will
+           be mostly 0/FAIL transitions or to put it another way mostly empty.
+           (Note that leaf nodes will not contain any transitions.)
+
+           This algorithm compresses the tables by eliminating most such
+           transitions, at the cost of a modest bit of extra work during lookup:
+
+           - Each states[] entry contains a .base field which indicates the
+           index in the state[] array wheres its transition data is stored.
+
+           - If .base is 0 there are no valid transitions from that node.
+
+           - If .base is nonzero then charid is added to it to find an entry in
+           the trans array.
+
+           -If trans[states[state].base+charid].check!=state then the
+           transition is taken to be a 0/Fail transition. Thus if there are fail
+           transitions at the front of the node then the .base offset will point
+           somewhere inside the previous nodes data (or maybe even into a node
+           even earlier), but the .check field determines if the transition is
+           valid.
+
+           XXX - wrong maybe?
+           The following process inplace converts the table to the compressed
+           table: We first do not compress the root node 1,and mark all its
+           .check pointers as 1 and set its .base pointer as 1 as well. This
+           allows us to do a DFA construction from the compressed table later,
+           and ensures that any .base pointers we calculate later are greater
+           than 0.
+
+           - We set 'pos' to indicate the first entry of the second node.
+
+           - We then iterate over the columns of the node, finding the first and
+           last used entry at l and m. We then copy l..m into pos..(pos+m-l),
+           and set the .check pointers accordingly, and advance pos
+           appropriately and repreat for the next node. Note that when we copy
+           the next pointers we have to convert them from the original
+           NODEIDX form to NODENUM form as the former is not valid post
+           compression.
+
+           - If a node has no transitions used we mark its base as 0 and do not
+           advance the pos pointer.
+
+           - If a node only has one transition we use a second pointer into the
+           structure to fill in allocated fail transitions from other states.
+           This pointer is independent of the main pointer and scans forward
+           looking for null transitions that are allocated to a state. When it
+           finds one it writes the single transition into the "hole".  If the
+           pointer doesnt find one the single transition is appended as normal.
+
+           - Once compressed we can Renew/realloc the structures to release the
+           excess space.
+
+           See "Table-Compression Methods" in sec 3.9 of the Red Dragon,
+           specifically Fig 3.47 and the associated pseudocode.
+
+           demq
+        */
+        const U32 laststate = TRIE_NODENUM( next_alloc );
+       U32 state, charid;
+        U32 pos = 0, zp=0;
+        trie->statecount = laststate;
+
+        for ( state = 1 ; state < laststate ; state++ ) {
+            U8 flag = 0;
+           const U32 stateidx = TRIE_NODEIDX( state );
+           const U32 o_used = trie->trans[ stateidx ].check;
+           U32 used = trie->trans[ stateidx ].check;
+            trie->trans[ stateidx ].check = 0;
+
+            for ( charid = 0;
+                  used && charid < trie->uniquecharcount;
+                  charid++ )
+            {
+                if ( flag || trie->trans[ stateidx + charid ].next ) {
+                    if ( trie->trans[ stateidx + charid ].next ) {
+                        if (o_used == 1) {
+                            for ( ; zp < pos ; zp++ ) {
+                                if ( ! trie->trans[ zp ].next ) {
+                                    break;
+                                }
+                            }
+                            trie->states[ state ].trans.base
+                                                    = zp
+                                                      + trie->uniquecharcount
+                                                      - charid ;
+                            trie->trans[ zp ].next
+                                = SAFE_TRIE_NODENUM( trie->trans[ stateidx
+                                                             + charid ].next );
+                            trie->trans[ zp ].check = state;
+                            if ( ++zp > pos ) pos = zp;
+                            break;
+                        }
+                        used--;
+                    }
+                    if ( !flag ) {
+                        flag = 1;
+                        trie->states[ state ].trans.base
+                                       = pos + trie->uniquecharcount - charid ;
+                    }
+                    trie->trans[ pos ].next
+                        = SAFE_TRIE_NODENUM(
+                                       trie->trans[ stateidx + charid ].next );
+                    trie->trans[ pos ].check = state;
+                    pos++;
+                }
+            }
+        }
+        trie->lasttrans = pos + 1;
+        trie->states = (reg_trie_state *)
+           PerlMemShared_realloc( trie->states, laststate
+                                  * sizeof(reg_trie_state) );
+        DEBUG_TRIE_COMPILE_MORE_r(
+            PerlIO_printf( Perl_debug_log,
+                "%*sAlloc: %d Orig: %"IVdf" elements, Final:%"IVdf". Savings of %%%5.2f\n",
+                (int)depth * 2 + 2,"",
+                (int)( ( TRIE_CHARCOUNT(trie) + 1 ) * trie->uniquecharcount
+                       + 1 ),
+                (IV)next_alloc,
+                (IV)pos,
+                ( ( next_alloc - pos ) * 100 ) / (double)next_alloc );
+            );
+
+        } /* end table compress */
+    }
+    DEBUG_TRIE_COMPILE_MORE_r(
+            PerlIO_printf(Perl_debug_log,
+                "%*sStatecount:%"UVxf" Lasttrans:%"UVxf"\n",
+                (int)depth * 2 + 2, "",
+                (UV)trie->statecount,
+                (UV)trie->lasttrans)
+    );
+    /* resize the trans array to remove unused space */
+    trie->trans = (reg_trie_trans *)
+       PerlMemShared_realloc( trie->trans, trie->lasttrans
+                              * sizeof(reg_trie_trans) );
+
+    {   /* Modify the program and insert the new TRIE node */
+        U8 nodetype =(U8)(flags & 0xFF);
+        char *str=NULL;
+
+#ifdef DEBUGGING
+        regnode *optimize = NULL;
+#ifdef RE_TRACK_PATTERN_OFFSETS
+
+        U32 mjd_offset = 0;
+        U32 mjd_nodelen = 0;
+#endif /* RE_TRACK_PATTERN_OFFSETS */
+#endif /* DEBUGGING */
+        /*
+           This means we convert either the first branch or the first Exact,
+           depending on whether the thing following (in 'last') is a branch
+           or not and whther first is the startbranch (ie is it a sub part of
+           the alternation or is it the whole thing.)
+           Assuming its a sub part we convert the EXACT otherwise we convert
+           the whole branch sequence, including the first.
+         */
+        /* Find the node we are going to overwrite */
+        if ( first != startbranch || OP( last ) == BRANCH ) {
+            /* branch sub-chain */
+            NEXT_OFF( first ) = (U16)(last - first);
+#ifdef RE_TRACK_PATTERN_OFFSETS
+            DEBUG_r({
+                mjd_offset= Node_Offset((convert));
+                mjd_nodelen= Node_Length((convert));
+            });
+#endif
+            /* whole branch chain */
+        }
+#ifdef RE_TRACK_PATTERN_OFFSETS
+        else {
+            DEBUG_r({
+                const  regnode *nop = NEXTOPER( convert );
+                mjd_offset= Node_Offset((nop));
+                mjd_nodelen= Node_Length((nop));
+            });
+        }
+        DEBUG_OPTIMISE_r(
+            PerlIO_printf(Perl_debug_log,
+                "%*sMJD offset:%"UVuf" MJD length:%"UVuf"\n",
+                (int)depth * 2 + 2, "",
+                (UV)mjd_offset, (UV)mjd_nodelen)
+        );
+#endif
+        /* But first we check to see if there is a common prefix we can
+           split out as an EXACT and put in front of the TRIE node.  */
+        trie->startstate= 1;
+        if ( trie->bitmap && !widecharmap && !trie->jump  ) {
+            U32 state;
+            for ( state = 1 ; state < trie->statecount-1 ; state++ ) {
+                U32 ofs = 0;
+                I32 idx = -1;
+                U32 count = 0;
+                const U32 base = trie->states[ state ].trans.base;
+
+                if ( trie->states[state].wordnum )
+                        count = 1;
+
+                for ( ofs = 0 ; ofs < trie->uniquecharcount ; ofs++ ) {
+                    if ( ( base + ofs >= trie->uniquecharcount ) &&
+                         ( base + ofs - trie->uniquecharcount < trie->lasttrans ) &&
+                         trie->trans[ base + ofs - trie->uniquecharcount ].check == state )
+                    {
+                        if ( ++count > 1 ) {
+                            SV **tmp = av_fetch( revcharmap, ofs, 0);
+                           const U8 *ch = (U8*)SvPV_nolen_const( *tmp );
+                            if ( state == 1 ) break;
+                            if ( count == 2 ) {
+                                Zero(trie->bitmap, ANYOF_BITMAP_SIZE, char);
+                                DEBUG_OPTIMISE_r(
+                                    PerlIO_printf(Perl_debug_log,
+                                       "%*sNew Start State=%"UVuf" Class: [",
+                                        (int)depth * 2 + 2, "",
+                                        (UV)state));
+                               if (idx >= 0) {
+                                   SV ** const tmp = av_fetch( revcharmap, idx, 0);
+                                   const U8 * const ch = (U8*)SvPV_nolen_const( *tmp );
+
+                                    TRIE_BITMAP_SET(trie,*ch);
+                                    if ( folder )
+                                        TRIE_BITMAP_SET(trie, folder[ *ch ]);
+                                    DEBUG_OPTIMISE_r(
+                                        PerlIO_printf(Perl_debug_log, "%s", (char*)ch)
+                                    );
+                               }
+                           }
+                           TRIE_BITMAP_SET(trie,*ch);
+                           if ( folder )
+                               TRIE_BITMAP_SET(trie,folder[ *ch ]);
+                           DEBUG_OPTIMISE_r(PerlIO_printf( Perl_debug_log,"%s", ch));
+                       }
+                        idx = ofs;
+                   }
+                }
+                if ( count == 1 ) {
+                    SV **tmp = av_fetch( revcharmap, idx, 0);
+                    STRLEN len;
+                    char *ch = SvPV( *tmp, len );
+                    DEBUG_OPTIMISE_r({
+                        SV *sv=sv_newmortal();
+                        PerlIO_printf( Perl_debug_log,
+                           "%*sPrefix State: %"UVuf" Idx:%"UVuf" Char='%s'\n",
+                            (int)depth * 2 + 2, "",
+                            (UV)state, (UV)idx,
+                            pv_pretty(sv, SvPV_nolen_const(*tmp), SvCUR(*tmp), 6,
+                               PL_colors[0], PL_colors[1],
+                               (SvUTF8(*tmp) ? PERL_PV_ESCAPE_UNI : 0) |
+                               PERL_PV_ESCAPE_FIRSTCHAR
+                            )
+                        );
+                    });
+                    if ( state==1 ) {
+                        OP( convert ) = nodetype;
+                        str=STRING(convert);
+                        STR_LEN(convert)=0;
+                    }
+                    STR_LEN(convert) += len;
+                    while (len--)
+                        *str++ = *ch++;
+               } else {
+#ifdef DEBUGGING
+                   if (state>1)
+                       DEBUG_OPTIMISE_r(PerlIO_printf( Perl_debug_log,"]\n"));
+#endif
+                   break;
+               }
+           }
+           trie->prefixlen = (state-1);
+            if (str) {
+                regnode *n = convert+NODE_SZ_STR(convert);
+                NEXT_OFF(convert) = NODE_SZ_STR(convert);
+                trie->startstate = state;
+                trie->minlen -= (state - 1);
+                trie->maxlen -= (state - 1);
+#ifdef DEBUGGING
+               /* At least the UNICOS C compiler choked on this
+                * being argument to DEBUG_r(), so let's just have
+                * it right here. */
+               if (
+#ifdef PERL_EXT_RE_BUILD
+                   1
+#else
+                   DEBUG_r_TEST
+#endif
+                   ) {
+                   regnode *fix = convert;
+                   U32 word = trie->wordcount;
+                   mjd_nodelen++;
+                   Set_Node_Offset_Length(convert, mjd_offset, state - 1);
+                   while( ++fix < n ) {
+                       Set_Node_Offset_Length(fix, 0, 0);
+                   }
+                   while (word--) {
+                       SV ** const tmp = av_fetch( trie_words, word, 0 );
+                       if (tmp) {
+                           if ( STR_LEN(convert) <= SvCUR(*tmp) )
+                               sv_chop(*tmp, SvPV_nolen(*tmp) + STR_LEN(convert));
+                           else
+                               sv_chop(*tmp, SvPV_nolen(*tmp) + SvCUR(*tmp));
+                       }
+                   }
+               }
+#endif
+                if (trie->maxlen) {
+                    convert = n;
+               } else {
+                    NEXT_OFF(convert) = (U16)(tail - convert);
+                    DEBUG_r(optimize= n);
+                }
+            }
+        }
+        if (!jumper)
+            jumper = last;
+        if ( trie->maxlen ) {
+           NEXT_OFF( convert ) = (U16)(tail - convert);
+           ARG_SET( convert, data_slot );
+           /* Store the offset to the first unabsorbed branch in
+              jump[0], which is otherwise unused by the jump logic.
+              We use this when dumping a trie and during optimisation. */
+           if (trie->jump)
+               trie->jump[0] = (U16)(nextbranch - convert);
+
+            /* If the start state is not accepting (meaning there is no empty string/NOTHING)
+            *   and there is a bitmap
+            *   and the first "jump target" node we found leaves enough room
+            * then convert the TRIE node into a TRIEC node, with the bitmap
+            * embedded inline in the opcode - this is hypothetically faster.
+            */
+            if ( !trie->states[trie->startstate].wordnum
+                && trie->bitmap
+                && ( (char *)jumper - (char *)convert) >= (int)sizeof(struct regnode_charclass) )
+            {
+                OP( convert ) = TRIEC;
+                Copy(trie->bitmap, ((struct regnode_charclass *)convert)->bitmap, ANYOF_BITMAP_SIZE, char);
+                PerlMemShared_free(trie->bitmap);
+                trie->bitmap= NULL;
+            } else
+                OP( convert ) = TRIE;
+
+            /* store the type in the flags */
+            convert->flags = nodetype;
+            DEBUG_r({
+            optimize = convert
+                      + NODE_STEP_REGNODE
+                      + regarglen[ OP( convert ) ];
+            });
+            /* XXX We really should free up the resource in trie now,
+                   as we won't use them - (which resources?) dmq */
+        }
+        /* needed for dumping*/
+        DEBUG_r(if (optimize) {
+            regnode *opt = convert;
+
+            while ( ++opt < optimize) {
+                Set_Node_Offset_Length(opt,0,0);
+            }
+            /*
+                Try to clean up some of the debris left after the
+                optimisation.
+             */
+            while( optimize < jumper ) {
+                mjd_nodelen += Node_Length((optimize));
+                OP( optimize ) = OPTIMIZED;
+                Set_Node_Offset_Length(optimize,0,0);
+                optimize++;
+            }
+            Set_Node_Offset_Length(convert,mjd_offset,mjd_nodelen);
+        });
+    } /* end node insert */
+
+    /*  Finish populating the prev field of the wordinfo array.  Walk back
+     *  from each accept state until we find another accept state, and if
+     *  so, point the first word's .prev field at the second word. If the
+     *  second already has a .prev field set, stop now. This will be the
+     *  case either if we've already processed that word's accept state,
+     *  or that state had multiple words, and the overspill words were
+     *  already linked up earlier.
+     */
+    {
+       U16 word;
+       U32 state;
+       U16 prev;
+
+       for (word=1; word <= trie->wordcount; word++) {
+           prev = 0;
+           if (trie->wordinfo[word].prev)
+               continue;
+           state = trie->wordinfo[word].accept;
+           while (state) {
+               state = prev_states[state];
+               if (!state)
+                   break;
+               prev = trie->states[state].wordnum;
+               if (prev)
+                   break;
+           }
+           trie->wordinfo[word].prev = prev;
+       }
+       Safefree(prev_states);
+    }
+
+
+    /* and now dump out the compressed format */
+    DEBUG_TRIE_COMPILE_r(dump_trie(trie, widecharmap, revcharmap, depth+1));
+
+    RExC_rxi->data->data[ data_slot + 1 ] = (void*)widecharmap;
+#ifdef DEBUGGING
+    RExC_rxi->data->data[ data_slot + TRIE_WORDS_OFFSET ] = (void*)trie_words;
+    RExC_rxi->data->data[ data_slot + 3 ] = (void*)revcharmap;
+#else
+    SvREFCNT_dec_NN(revcharmap);
+#endif
+    return trie->jump
+           ? MADE_JUMP_TRIE
+           : trie->startstate>1
+             ? MADE_EXACT_TRIE
+             : MADE_TRIE;
+}
+
+STATIC void
+S_make_trie_failtable(pTHX_ RExC_state_t *pRExC_state, regnode *source,  regnode *stclass, U32 depth)
+{
+/* The Trie is constructed and compressed now so we can build a fail array if
+ * it's needed
+
+   This is basically the Aho-Corasick algorithm. Its from exercise 3.31 and
+   3.32 in the
+   "Red Dragon" -- Compilers, principles, techniques, and tools. Aho, Sethi,
+   Ullman 1985/88
+   ISBN 0-201-10088-6
+
+   We find the fail state for each state in the trie, this state is the longest
+   proper suffix of the current state's 'word' that is also a proper prefix of
+   another word in our trie. State 1 represents the word '' and is thus the
+   default fail state. This allows the DFA not to have to restart after its
+   tried and failed a word at a given point, it simply continues as though it
+   had been matching the other word in the first place.
+   Consider
+      'abcdgu'=~/abcdefg|cdgu/
+   When we get to 'd' we are still matching the first word, we would encounter
+   'g' which would fail, which would bring us to the state representing 'd' in
+   the second word where we would try 'g' and succeed, proceeding to match
+   'cdgu'.
+ */
+ /* add a fail transition */
+    const U32 trie_offset = ARG(source);
+    reg_trie_data *trie=(reg_trie_data *)RExC_rxi->data->data[trie_offset];
+    U32 *q;
+    const U32 ucharcount = trie->uniquecharcount;
+    const U32 numstates = trie->statecount;
+    const U32 ubound = trie->lasttrans + ucharcount;
+    U32 q_read = 0;
+    U32 q_write = 0;
+    U32 charid;
+    U32 base = trie->states[ 1 ].trans.base;
+    U32 *fail;
+    reg_ac_data *aho;
+    const U32 data_slot = add_data( pRExC_state, STR_WITH_LEN("T"));
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_MAKE_TRIE_FAILTABLE;
+#ifndef DEBUGGING
+    PERL_UNUSED_ARG(depth);
+#endif
+
+
+    ARG_SET( stclass, data_slot );
+    aho = (reg_ac_data *) PerlMemShared_calloc( 1, sizeof(reg_ac_data) );
+    RExC_rxi->data->data[ data_slot ] = (void*)aho;
+    aho->trie=trie_offset;
+    aho->states=(reg_trie_state *)PerlMemShared_malloc( numstates * sizeof(reg_trie_state) );
+    Copy( trie->states, aho->states, numstates, reg_trie_state );
+    Newxz( q, numstates, U32);
+    aho->fail = (U32 *) PerlMemShared_calloc( numstates, sizeof(U32) );
+    aho->refcount = 1;
+    fail = aho->fail;
+    /* initialize fail[0..1] to be 1 so that we always have
+       a valid final fail state */
+    fail[ 0 ] = fail[ 1 ] = 1;
+
+    for ( charid = 0; charid < ucharcount ; charid++ ) {
+       const U32 newstate = TRIE_TRANS_STATE( 1, base, ucharcount, charid, 0 );
+       if ( newstate ) {
+            q[ q_write ] = newstate;
+            /* set to point at the root */
+            fail[ q[ q_write++ ] ]=1;
+        }
+    }
+    while ( q_read < q_write) {
+       const U32 cur = q[ q_read++ % numstates ];
+        base = trie->states[ cur ].trans.base;
+
+        for ( charid = 0 ; charid < ucharcount ; charid++ ) {
+           const U32 ch_state = TRIE_TRANS_STATE( cur, base, ucharcount, charid, 1 );
+           if (ch_state) {
+                U32 fail_state = cur;
+                U32 fail_base;
+                do {
+                    fail_state = fail[ fail_state ];
+                    fail_base = aho->states[ fail_state ].trans.base;
+                } while ( !TRIE_TRANS_STATE( fail_state, fail_base, ucharcount, charid, 1 ) );
+
+                fail_state = TRIE_TRANS_STATE( fail_state, fail_base, ucharcount, charid, 1 );
+                fail[ ch_state ] = fail_state;
+                if ( !aho->states[ ch_state ].wordnum && aho->states[ fail_state ].wordnum )
+                {
+                        aho->states[ ch_state ].wordnum =  aho->states[ fail_state ].wordnum;
+                }
+                q[ q_write++ % numstates] = ch_state;
+            }
+        }
+    }
+    /* restore fail[0..1] to 0 so that we "fall out" of the AC loop
+       when we fail in state 1, this allows us to use the
+       charclass scan to find a valid start char. This is based on the principle
+       that theres a good chance the string being searched contains lots of stuff
+       that cant be a start char.
+     */
+    fail[ 0 ] = fail[ 1 ] = 0;
+    DEBUG_TRIE_COMPILE_r({
+        PerlIO_printf(Perl_debug_log,
+                     "%*sStclass Failtable (%"UVuf" states): 0",
+                     (int)(depth * 2), "", (UV)numstates
+        );
+        for( q_read=1; q_read<numstates; q_read++ ) {
+            PerlIO_printf(Perl_debug_log, ", %"UVuf, (UV)fail[q_read]);
+        }
+        PerlIO_printf(Perl_debug_log, "\n");
+    });
+    Safefree(q);
+    /*RExC_seen |= REG_TRIEDFA_SEEN;*/
+}
+
+
+#define DEBUG_PEEP(str,scan,depth) \
+    DEBUG_OPTIMISE_r({if (scan){ \
+       SV * const mysv=sv_newmortal(); \
+       regnode *Next = regnext(scan); \
+       regprop(RExC_rx, mysv, scan, NULL); \
+       PerlIO_printf(Perl_debug_log, "%*s" str ">%3d: %s (%d)\n", \
+       (int)depth*2, "", REG_NODE_NUM(scan), SvPV_nolen_const(mysv),\
+       Next ? (REG_NODE_NUM(Next)) : 0 ); \
+   }});
+
+
+/* The below joins as many adjacent EXACTish nodes as possible into a single
+ * one.  The regop may be changed if the node(s) contain certain sequences that
+ * require special handling.  The joining is only done if:
+ * 1) there is room in the current conglomerated node to entirely contain the
+ *    next one.
+ * 2) they are the exact same node type
+ *
+ * The adjacent nodes actually may be separated by NOTHING-kind nodes, and
+ * these get optimized out
+ *
+ * If a node is to match under /i (folded), the number of characters it matches
+ * can be different than its character length if it contains a multi-character
+ * fold.  *min_subtract is set to the total delta number of characters of the
+ * input nodes.
+ *
+ * And *unfolded_multi_char is set to indicate whether or not the node contains
+ * an unfolded multi-char fold.  This happens when whether the fold is valid or
+ * not won't be known until runtime; namely for EXACTF nodes that contain LATIN
+ * SMALL LETTER SHARP S, as only if the target string being matched against
+ * turns out to be UTF-8 is that fold valid; and also for EXACTFL nodes whose
+ * folding rules depend on the locale in force at runtime.  (Multi-char folds
+ * whose components are all above the Latin1 range are not run-time locale
+ * dependent, and have already been folded by the time this function is
+ * called.)
+ *
+ * This is as good a place as any to discuss the design of handling these
+ * multi-character fold sequences.  It's been wrong in Perl for a very long
+ * time.  There are three code points in Unicode whose multi-character folds
+ * were long ago discovered to mess things up.  The previous designs for
+ * dealing with these involved assigning a special node for them.  This
+ * approach doesn't always work, as evidenced by this example:
+ *      "\xDFs" =~ /s\xDF/ui    # Used to fail before these patches
+ * Both sides fold to "sss", but if the pattern is parsed to create a node that
+ * would match just the \xDF, it won't be able to handle the case where a
+ * successful match would have to cross the node's boundary.  The new approach
+ * that hopefully generally solves the problem generates an EXACTFU_SS node
+ * that is "sss" in this case.
+ *
+ * It turns out that there are problems with all multi-character folds, and not
+ * just these three.  Now the code is general, for all such cases.  The
+ * approach taken is:
+ * 1)   This routine examines each EXACTFish node that could contain multi-
+ *      character folded sequences.  Since a single character can fold into
+ *      such a sequence, the minimum match length for this node is less than
+ *      the number of characters in the node.  This routine returns in
+ *      *min_subtract how many characters to subtract from the the actual
+ *      length of the string to get a real minimum match length; it is 0 if
+ *      there are no multi-char foldeds.  This delta is used by the caller to
+ *      adjust the min length of the match, and the delta between min and max,
+ *      so that the optimizer doesn't reject these possibilities based on size
+ *      constraints.
+ * 2)   For the sequence involving the Sharp s (\xDF), the node type EXACTFU_SS
+ *      is used for an EXACTFU node that contains at least one "ss" sequence in
+ *      it.  For non-UTF-8 patterns and strings, this is the only case where
+ *      there is a possible fold length change.  That means that a regular
+ *      EXACTFU node without UTF-8 involvement doesn't have to concern itself
+ *      with length changes, and so can be processed faster.  regexec.c takes
+ *      advantage of this.  Generally, an EXACTFish node that is in UTF-8 is
+ *      pre-folded by regcomp.c (except EXACTFL, some of whose folds aren't
+ *      known until runtime).  This saves effort in regex matching.  However,
+ *      the pre-folding isn't done for non-UTF8 patterns because the fold of
+ *      the MICRO SIGN requires UTF-8, and we don't want to slow things down by
+ *      forcing the pattern into UTF8 unless necessary.  Also what EXACTF (and,
+ *      again, EXACTFL) nodes fold to isn't known until runtime.  The fold
+ *      possibilities for the non-UTF8 patterns are quite simple, except for
+ *      the sharp s.  All the ones that don't involve a UTF-8 target string are
+ *      members of a fold-pair, and arrays are set up for all of them so that
+ *      the other member of the pair can be found quickly.  Code elsewhere in
+ *      this file makes sure that in EXACTFU nodes, the sharp s gets folded to
+ *      'ss', even if the pattern isn't UTF-8.  This avoids the issues
+ *      described in the next item.
+ * 3)   A problem remains for unfolded multi-char folds. (These occur when the
+ *      validity of the fold won't be known until runtime, and so must remain
+ *      unfolded for now.  This happens for the sharp s in EXACTF and EXACTFA
+ *      nodes when the pattern isn't in UTF-8.  (Note, BTW, that there cannot
+ *      be an EXACTF node with a UTF-8 pattern.)  They also occur for various
+ *      folds in EXACTFL nodes, regardless of the UTF-ness of the pattern.)
+ *      The reason this is a problem is that the optimizer part of regexec.c
+ *      (probably unwittingly, in Perl_regexec_flags()) makes an assumption
+ *      that a character in the pattern corresponds to at most a single
+ *      character in the target string.  (And I do mean character, and not byte
+ *      here, unlike other parts of the documentation that have never been
+ *      updated to account for multibyte Unicode.)  sharp s in EXACTF and
+ *      EXACTFL nodes can match the two character string 'ss'; in EXACTFA nodes
+ *      it can match "\x{17F}\x{17F}".  These, along with other ones in EXACTFL
+ *      nodes, violate the assumption, and they are the only instances where it
+ *      is violated.  I'm reluctant to try to change the assumption, as the
+ *      code involved is impenetrable to me (khw), so instead the code here
+ *      punts.  This routine examines EXACTFL nodes, and (when the pattern
+ *      isn't UTF-8) EXACTF and EXACTFA for such unfolded folds, and returns a
+ *      boolean indicating whether or not the node contains such a fold.  When
+ *      it is true, the caller sets a flag that later causes the optimizer in
+ *      this file to not set values for the floating and fixed string lengths,
+ *      and thus avoids the optimizer code in regexec.c that makes the invalid
+ *      assumption.  Thus, there is no optimization based on string lengths for
+ *      EXACTFL nodes that contain these few folds, nor for non-UTF8-pattern
+ *      EXACTF and EXACTFA nodes that contain the sharp s.  (The reason the
+ *      assumption is wrong only in these cases is that all other non-UTF-8
+ *      folds are 1-1; and, for UTF-8 patterns, we pre-fold all other folds to
+ *      their expanded versions.  (Again, we can't prefold sharp s to 'ss' in
+ *      EXACTF nodes because we don't know at compile time if it actually
+ *      matches 'ss' or not.  For EXACTF nodes it will match iff the target
+ *      string is in UTF-8.  This is in contrast to EXACTFU nodes, where it
+ *      always matches; and EXACTFA where it never does.  In an EXACTFA node in
+ *      a UTF-8 pattern, sharp s is folded to "\x{17F}\x{17F}, avoiding the
+ *      problem; but in a non-UTF8 pattern, folding it to that above-Latin1
+ *      string would require the pattern to be forced into UTF-8, the overhead
+ *      of which we want to avoid.  Similarly the unfolded multi-char folds in
+ *      EXACTFL nodes will match iff the locale at the time of match is a UTF-8
+ *      locale.)
+ *
+ *      Similarly, the code that generates tries doesn't currently handle
+ *      not-already-folded multi-char folds, and it looks like a pain to change
+ *      that.  Therefore, trie generation of EXACTFA nodes with the sharp s
+ *      doesn't work.  Instead, such an EXACTFA is turned into a new regnode,
+ *      EXACTFA_NO_TRIE, which the trie code knows not to handle.  Most people
+ *      using /iaa matching will be doing so almost entirely with ASCII
+ *      strings, so this should rarely be encountered in practice */
+
+#define JOIN_EXACT(scan,min_subtract,unfolded_multi_char, flags) \
+    if (PL_regkind[OP(scan)] == EXACT) \
+        join_exact(pRExC_state,(scan),(min_subtract),unfolded_multi_char, (flags),NULL,depth+1)
+
+STATIC U32
+S_join_exact(pTHX_ RExC_state_t *pRExC_state, regnode *scan,
+                   UV *min_subtract, bool *unfolded_multi_char,
+                   U32 flags,regnode *val, U32 depth)
+{
+    /* Merge several consecutive EXACTish nodes into one. */
+    regnode *n = regnext(scan);
+    U32 stringok = 1;
+    regnode *next = scan + NODE_SZ_STR(scan);
+    U32 merged = 0;
+    U32 stopnow = 0;
+#ifdef DEBUGGING
+    regnode *stop = scan;
+    GET_RE_DEBUG_FLAGS_DECL;
+#else
+    PERL_UNUSED_ARG(depth);
+#endif
+
+    PERL_ARGS_ASSERT_JOIN_EXACT;
+#ifndef EXPERIMENTAL_INPLACESCAN
+    PERL_UNUSED_ARG(flags);
+    PERL_UNUSED_ARG(val);
+#endif
+    DEBUG_PEEP("join",scan,depth);
+
+    /* Look through the subsequent nodes in the chain.  Skip NOTHING, merge
+     * EXACT ones that are mergeable to the current one. */
+    while (n
+           && (PL_regkind[OP(n)] == NOTHING
+               || (stringok && OP(n) == OP(scan)))
+           && NEXT_OFF(n)
+           && NEXT_OFF(scan) + NEXT_OFF(n) < I16_MAX)
+    {
+
+        if (OP(n) == TAIL || n > next)
+            stringok = 0;
+        if (PL_regkind[OP(n)] == NOTHING) {
+            DEBUG_PEEP("skip:",n,depth);
+            NEXT_OFF(scan) += NEXT_OFF(n);
+            next = n + NODE_STEP_REGNODE;
+#ifdef DEBUGGING
+            if (stringok)
+                stop = n;
+#endif
+            n = regnext(n);
+        }
+        else if (stringok) {
+            const unsigned int oldl = STR_LEN(scan);
+            regnode * const nnext = regnext(n);
+
+            /* XXX I (khw) kind of doubt that this works on platforms (should
+             * Perl ever run on one) where U8_MAX is above 255 because of lots
+             * of other assumptions */
+            /* Don't join if the sum can't fit into a single node */
+            if (oldl + STR_LEN(n) > U8_MAX)
+                break;
+
+            DEBUG_PEEP("merg",n,depth);
+            merged++;
+
+            NEXT_OFF(scan) += NEXT_OFF(n);
+            STR_LEN(scan) += STR_LEN(n);
+            next = n + NODE_SZ_STR(n);
+            /* Now we can overwrite *n : */
+            Move(STRING(n), STRING(scan) + oldl, STR_LEN(n), char);
+#ifdef DEBUGGING
+            stop = next - 1;
+#endif
+            n = nnext;
+            if (stopnow) break;
+        }
+
+#ifdef EXPERIMENTAL_INPLACESCAN
+       if (flags && !NEXT_OFF(n)) {
+           DEBUG_PEEP("atch", val, depth);
+           if (reg_off_by_arg[OP(n)]) {
+               ARG_SET(n, val - n);
+           }
+           else {
+               NEXT_OFF(n) = val - n;
+           }
+           stopnow = 1;
+       }
+#endif
+    }
+
+    *min_subtract = 0;
+    *unfolded_multi_char = FALSE;
+
+    /* Here, all the adjacent mergeable EXACTish nodes have been merged.  We
+     * can now analyze for sequences of problematic code points.  (Prior to
+     * this final joining, sequences could have been split over boundaries, and
+     * hence missed).  The sequences only happen in folding, hence for any
+     * non-EXACT EXACTish node */
+    if (OP(scan) != EXACT) {
+        U8* s0 = (U8*) STRING(scan);
+        U8* s = s0;
+        U8* s_end = s0 + STR_LEN(scan);
+
+        int total_count_delta = 0;  /* Total delta number of characters that
+                                       multi-char folds expand to */
+
+       /* One pass is made over the node's string looking for all the
+        * possibilities.  To avoid some tests in the loop, there are two main
+        * cases, for UTF-8 patterns (which can't have EXACTF nodes) and
+        * non-UTF-8 */
+       if (UTF) {
+            U8* folded = NULL;
+
+            if (OP(scan) == EXACTFL) {
+                U8 *d;
+
+                /* An EXACTFL node would already have been changed to another
+                 * node type unless there is at least one character in it that
+                 * is problematic; likely a character whose fold definition
+                 * won't be known until runtime, and so has yet to be folded.
+                 * For all but the UTF-8 locale, folds are 1-1 in length, but
+                 * to handle the UTF-8 case, we need to create a temporary
+                 * folded copy using UTF-8 locale rules in order to analyze it.
+                 * This is because our macros that look to see if a sequence is
+                 * a multi-char fold assume everything is folded (otherwise the
+                 * tests in those macros would be too complicated and slow).
+                 * Note that here, the non-problematic folds will have already
+                 * been done, so we can just copy such characters.  We actually
+                 * don't completely fold the EXACTFL string.  We skip the
+                 * unfolded multi-char folds, as that would just create work
+                 * below to figure out the size they already are */
+
+                Newx(folded, UTF8_MAX_FOLD_CHAR_EXPAND * STR_LEN(scan) + 1, U8);
+                d = folded;
+                while (s < s_end) {
+                    STRLEN s_len = UTF8SKIP(s);
+                    if (! is_PROBLEMATIC_LOCALE_FOLD_utf8(s)) {
+                        Copy(s, d, s_len, U8);
+                        d += s_len;
+                    }
+                    else if (is_FOLDS_TO_MULTI_utf8(s)) {
+                        *unfolded_multi_char = TRUE;
+                        Copy(s, d, s_len, U8);
+                        d += s_len;
+                    }
+                    else if (isASCII(*s)) {
+                        *(d++) = toFOLD(*s);
+                    }
+                    else {
+                        STRLEN len;
+                        _to_utf8_fold_flags(s, d, &len, FOLD_FLAGS_FULL);
+                        d += len;
+                    }
+                    s += s_len;
+                }
+
+                /* Point the remainder of the routine to look at our temporary
+                 * folded copy */
+                s = folded;
+                s_end = d;
+            } /* End of creating folded copy of EXACTFL string */
+
+            /* Examine the string for a multi-character fold sequence.  UTF-8
+             * patterns have all characters pre-folded by the time this code is
+             * executed */
+            while (s < s_end - 1) /* Can stop 1 before the end, as minimum
+                                     length sequence we are looking for is 2 */
+           {
+                int count = 0;  /* How many characters in a multi-char fold */
+                int len = is_MULTI_CHAR_FOLD_utf8_safe(s, s_end);
+                if (! len) {    /* Not a multi-char fold: get next char */
+                    s += UTF8SKIP(s);
+                    continue;
+                }
+
+                /* Nodes with 'ss' require special handling, except for
+                 * EXACTFA-ish for which there is no multi-char fold to this */
+                if (len == 2 && *s == 's' && *(s+1) == 's'
+                    && OP(scan) != EXACTFA
+                    && OP(scan) != EXACTFA_NO_TRIE)
+                {
+                    count = 2;
+                    if (OP(scan) != EXACTFL) {
+                        OP(scan) = EXACTFU_SS;
+                    }
+                    s += 2;
+                }
+                else { /* Here is a generic multi-char fold. */
+                    U8* multi_end  = s + len;
+
+                    /* Count how many characters in it.  In the case of /aa, no
+                     * folds which contain ASCII code points are allowed, so
+                     * check for those, and skip if found. */
+                    if (OP(scan) != EXACTFA && OP(scan) != EXACTFA_NO_TRIE) {
+                        count = utf8_length(s, multi_end);
+                        s = multi_end;
+                    }
+                    else {
+                        while (s < multi_end) {
+                            if (isASCII(*s)) {
+                                s++;
+                                goto next_iteration;
+                            }
+                            else {
+                                s += UTF8SKIP(s);
+                            }
+                            count++;
+                        }
+                    }
+                }
+
+                /* The delta is how long the sequence is minus 1 (1 is how long
+                 * the character that folds to the sequence is) */
+                total_count_delta += count - 1;
+              next_iteration: ;
+           }
+
+            /* We created a temporary folded copy of the string in EXACTFL
+             * nodes.  Therefore we need to be sure it doesn't go below zero,
+             * as the real string could be shorter */
+            if (OP(scan) == EXACTFL) {
+                int total_chars = utf8_length((U8*) STRING(scan),
+                                           (U8*) STRING(scan) + STR_LEN(scan));
+                if (total_count_delta > total_chars) {
+                    total_count_delta = total_chars;
+                }
+            }
+
+            *min_subtract += total_count_delta;
+            Safefree(folded);
+       }
+       else if (OP(scan) == EXACTFA) {
+
+            /* Non-UTF-8 pattern, EXACTFA node.  There can't be a multi-char
+             * fold to the ASCII range (and there are no existing ones in the
+             * upper latin1 range).  But, as outlined in the comments preceding
+             * this function, we need to flag any occurrences of the sharp s.
+             * This character forbids trie formation (because of added
+             * complexity) */
+           while (s < s_end) {
+                if (*s == LATIN_SMALL_LETTER_SHARP_S) {
+                    OP(scan) = EXACTFA_NO_TRIE;
+                    *unfolded_multi_char = TRUE;
+                    break;
+                }
+                s++;
+                continue;
+            }
+        }
+       else {
+
+            /* Non-UTF-8 pattern, not EXACTFA node.  Look for the multi-char
+             * folds that are all Latin1.  As explained in the comments
+             * preceding this function, we look also for the sharp s in EXACTF
+             * and EXACTFL nodes; it can be in the final position.  Otherwise
+             * we can stop looking 1 byte earlier because have to find at least
+             * two characters for a multi-fold */
+           const U8* upper = (OP(scan) == EXACTF || OP(scan) == EXACTFL)
+                              ? s_end
+                              : s_end -1;
+
+           while (s < upper) {
+                int len = is_MULTI_CHAR_FOLD_latin1_safe(s, s_end);
+                if (! len) {    /* Not a multi-char fold. */
+                    if (*s == LATIN_SMALL_LETTER_SHARP_S
+                        && (OP(scan) == EXACTF || OP(scan) == EXACTFL))
+                    {
+                        *unfolded_multi_char = TRUE;
+                    }
+                    s++;
+                    continue;
+                }
+
+                if (len == 2
+                    && isARG2_lower_or_UPPER_ARG1('s', *s)
+                    && isARG2_lower_or_UPPER_ARG1('s', *(s+1)))
+                {
+
+                    /* EXACTF nodes need to know that the minimum length
+                     * changed so that a sharp s in the string can match this
+                     * ss in the pattern, but they remain EXACTF nodes, as they
+                     * won't match this unless the target string is is UTF-8,
+                     * which we don't know until runtime.  EXACTFL nodes can't
+                     * transform into EXACTFU nodes */
+                    if (OP(scan) != EXACTF && OP(scan) != EXACTFL) {
+                        OP(scan) = EXACTFU_SS;
+                    }
+               }
+
+                *min_subtract += len - 1;
+                s += len;
+           }
+       }
+    }
+
+#ifdef DEBUGGING
+    /* Allow dumping but overwriting the collection of skipped
+     * ops and/or strings with fake optimized ops */
+    n = scan + NODE_SZ_STR(scan);
+    while (n <= stop) {
+       OP(n) = OPTIMIZED;
+       FLAGS(n) = 0;
+       NEXT_OFF(n) = 0;
+        n++;
+    }
+#endif
+    DEBUG_OPTIMISE_r(if (merged){DEBUG_PEEP("finl",scan,depth)});
+    return stopnow;
+}
+
+/* REx optimizer.  Converts nodes into quicker variants "in place".
+   Finds fixed substrings.  */
+
+/* Stops at toplevel WHILEM as well as at "last". At end *scanp is set
+   to the position after last scanned or to NULL. */
+
+#define INIT_AND_WITHP \
+    assert(!and_withp); \
+    Newx(and_withp,1, regnode_ssc); \
+    SAVEFREEPV(and_withp)
+
+/* this is a chain of data about sub patterns we are processing that
+   need to be handled separately/specially in study_chunk. Its so
+   we can simulate recursion without losing state.  */
+struct scan_frame;
+typedef struct scan_frame {
+    regnode *last;  /* last node to process in this frame */
+    regnode *next;  /* next node to process when last is reached */
+    struct scan_frame *prev; /*previous frame*/
+    U32 prev_recursed_depth;
+    I32 stop; /* what stopparen do we use */
+} scan_frame;
+
+
+STATIC SSize_t
+S_study_chunk(pTHX_ RExC_state_t *pRExC_state, regnode **scanp,
+                        SSize_t *minlenp, SSize_t *deltap,
+                       regnode *last,
+                       scan_data_t *data,
+                       I32 stopparen,
+                        U32 recursed_depth,
+                       regnode_ssc *and_withp,
+                       U32 flags, U32 depth)
+                       /* scanp: Start here (read-write). */
+                       /* deltap: Write maxlen-minlen here. */
+                       /* last: Stop before this one. */
+                       /* data: string data about the pattern */
+                       /* stopparen: treat close N as END */
+                       /* recursed: which subroutines have we recursed into */
+                       /* and_withp: Valid if flags & SCF_DO_STCLASS_OR */
+{
+    dVAR;
+    /* There must be at least this number of characters to match */
+    SSize_t min = 0;
+    I32 pars = 0, code;
+    regnode *scan = *scanp, *next;
+    SSize_t delta = 0;
+    int is_inf = (flags & SCF_DO_SUBSTR) && (data->flags & SF_IS_INF);
+    int is_inf_internal = 0;           /* The studied chunk is infinite */
+    I32 is_par = OP(scan) == OPEN ? ARG(scan) : 0;
+    scan_data_t data_fake;
+    SV *re_trie_maxbuff = NULL;
+    regnode *first_non_open = scan;
+    SSize_t stopmin = SSize_t_MAX;
+    scan_frame *frame = NULL;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_STUDY_CHUNK;
+
+#ifdef DEBUGGING
+    StructCopy(&zero_scan_data, &data_fake, scan_data_t);
+#endif
+    if ( depth == 0 ) {
+        while (first_non_open && OP(first_non_open) == OPEN)
+            first_non_open=regnext(first_non_open);
+    }
+
+
+  fake_study_recurse:
+    while ( scan && OP(scan) != END && scan < last ){
+        UV min_subtract = 0;    /* How mmany chars to subtract from the minimum
+                                   node length to get a real minimum (because
+                                   the folded version may be shorter) */
+       bool unfolded_multi_char = FALSE;
+       /* Peephole optimizer: */
+        DEBUG_OPTIMISE_MORE_r(
+        {
+            PerlIO_printf(Perl_debug_log,
+                "%*sstudy_chunk stopparen=%ld depth=%lu recursed_depth=%lu ",
+                ((int) depth*2), "", (long)stopparen,
+                (unsigned long)depth, (unsigned long)recursed_depth);
+            if (recursed_depth) {
+                U32 i;
+                U32 j;
+                for ( j = 0 ; j < recursed_depth ; j++ ) {
+                    PerlIO_printf(Perl_debug_log,"[");
+                    for ( i = 0 ; i < (U32)RExC_npar ; i++ )
+                        PerlIO_printf(Perl_debug_log,"%d",
+                            PAREN_TEST(RExC_study_chunk_recursed +
+                                       (j * RExC_study_chunk_recursed_bytes), i)
+                            ? 1 : 0
+                        );
+                    PerlIO_printf(Perl_debug_log,"]");
+                }
+            }
+            PerlIO_printf(Perl_debug_log,"\n");
+        }
+        );
+        DEBUG_STUDYDATA("Peep:", data, depth);
+        DEBUG_PEEP("Peep", scan, depth);
+
+
+        /* The reason we do this here we need to deal with things like /(?:f)(?:o)(?:o)/
+         * which cant be dealt with by the normal EXACT parsing code, as each (?:..) is handled
+         * by a different invocation of reg() -- Yves
+         */
+        JOIN_EXACT(scan,&min_subtract, &unfolded_multi_char, 0);
+
+       /* Follow the next-chain of the current node and optimize
+          away all the NOTHINGs from it.  */
+       if (OP(scan) != CURLYX) {
+           const int max = (reg_off_by_arg[OP(scan)]
+                      ? I32_MAX
+                      /* I32 may be smaller than U16 on CRAYs! */
+                      : (I32_MAX < U16_MAX ? I32_MAX : U16_MAX));
+           int off = (reg_off_by_arg[OP(scan)] ? ARG(scan) : NEXT_OFF(scan));
+           int noff;
+           regnode *n = scan;
+
+           /* Skip NOTHING and LONGJMP. */
+           while ((n = regnext(n))
+                  && ((PL_regkind[OP(n)] == NOTHING && (noff = NEXT_OFF(n)))
+                      || ((OP(n) == LONGJMP) && (noff = ARG(n))))
+                  && off + noff < max)
+               off += noff;
+           if (reg_off_by_arg[OP(scan)])
+               ARG(scan) = off;
+           else
+               NEXT_OFF(scan) = off;
+       }
+
+
+
+       /* The principal pseudo-switch.  Cannot be a switch, since we
+          look into several different things.  */
+       if (OP(scan) == BRANCH || OP(scan) == BRANCHJ
+                  || OP(scan) == IFTHEN) {
+           next = regnext(scan);
+           code = OP(scan);
+            /* demq: the op(next)==code check is to see if we have
+             * "branch-branch" AFAICT */
+
+           if (OP(next) == code || code == IFTHEN) {
+                /* NOTE - There is similar code to this block below for
+                 * handling TRIE nodes on a re-study.  If you change stuff here
+                 * check there too. */
+               SSize_t max1 = 0, min1 = SSize_t_MAX, num = 0;
+               regnode_ssc accum;
+               regnode * const startbranch=scan;
+
+                if (flags & SCF_DO_SUBSTR) {
+                    /* Cannot merge strings after this. */
+                    scan_commit(pRExC_state, data, minlenp, is_inf);
+                }
+
+                if (flags & SCF_DO_STCLASS)
+                   ssc_init_zero(pRExC_state, &accum);
+
+               while (OP(scan) == code) {
+                   SSize_t deltanext, minnext, fake;
+                   I32 f = 0;
+                   regnode_ssc this_class;
+
+                   num++;
+                   data_fake.flags = 0;
+                   if (data) {
+                       data_fake.whilem_c = data->whilem_c;
+                       data_fake.last_closep = data->last_closep;
+                   }
+                   else
+                       data_fake.last_closep = &fake;
+
+                   data_fake.pos_delta = delta;
+                   next = regnext(scan);
+                   scan = NEXTOPER(scan);
+                   if (code != BRANCH)
+                       scan = NEXTOPER(scan);
+                   if (flags & SCF_DO_STCLASS) {
+                       ssc_init(pRExC_state, &this_class);
+                       data_fake.start_class = &this_class;
+                       f = SCF_DO_STCLASS_AND;
+                   }
+                   if (flags & SCF_WHILEM_VISITED_POS)
+                       f |= SCF_WHILEM_VISITED_POS;
+
+                   /* we suppose the run is continuous, last=next...*/
+                   minnext = study_chunk(pRExC_state, &scan, minlenp,
+                                      &deltanext, next, &data_fake, stopparen,
+                                      recursed_depth, NULL, f,depth+1);
+                   if (min1 > minnext)
+                       min1 = minnext;
+                   if (deltanext == SSize_t_MAX) {
+                       is_inf = is_inf_internal = 1;
+                       max1 = SSize_t_MAX;
+                   } else if (max1 < minnext + deltanext)
+                       max1 = minnext + deltanext;
+                   scan = next;
+                   if (data_fake.flags & (SF_HAS_PAR|SF_IN_PAR))
+                       pars++;
+                   if (data_fake.flags & SCF_SEEN_ACCEPT) {
+                       if ( stopmin > minnext)
+                           stopmin = min + min1;
+                       flags &= ~SCF_DO_SUBSTR;
+                       if (data)
+                           data->flags |= SCF_SEEN_ACCEPT;
+                   }
+                   if (data) {
+                       if (data_fake.flags & SF_HAS_EVAL)
+                           data->flags |= SF_HAS_EVAL;
+                       data->whilem_c = data_fake.whilem_c;
+                   }
+                   if (flags & SCF_DO_STCLASS)
+                       ssc_or(pRExC_state, &accum, (regnode_charclass*)&this_class);
+               }
+               if (code == IFTHEN && num < 2) /* Empty ELSE branch */
+                   min1 = 0;
+               if (flags & SCF_DO_SUBSTR) {
+                   data->pos_min += min1;
+                   if (data->pos_delta >= SSize_t_MAX - (max1 - min1))
+                       data->pos_delta = SSize_t_MAX;
+                   else
+                       data->pos_delta += max1 - min1;
+                   if (max1 != min1 || is_inf)
+                       data->longest = &(data->longest_float);
+               }
+               min += min1;
+               if (delta == SSize_t_MAX
+                || SSize_t_MAX - delta - (max1 - min1) < 0)
+                   delta = SSize_t_MAX;
+               else
+                   delta += max1 - min1;
+               if (flags & SCF_DO_STCLASS_OR) {
+                   ssc_or(pRExC_state, data->start_class, (regnode_charclass*) &accum);
+                   if (min1) {
+                       ssc_and(pRExC_state, data->start_class, (regnode_charclass *) and_withp);
+                       flags &= ~SCF_DO_STCLASS;
+                   }
+               }
+               else if (flags & SCF_DO_STCLASS_AND) {
+                   if (min1) {
+                       ssc_and(pRExC_state, data->start_class, (regnode_charclass *) &accum);
+                       flags &= ~SCF_DO_STCLASS;
+                   }
+                   else {
+                       /* Switch to OR mode: cache the old value of
+                        * data->start_class */
+                       INIT_AND_WITHP;
+                       StructCopy(data->start_class, and_withp, regnode_ssc);
+                       flags &= ~SCF_DO_STCLASS_AND;
+                       StructCopy(&accum, data->start_class, regnode_ssc);
+                       flags |= SCF_DO_STCLASS_OR;
+                   }
+               }
+
+                if (PERL_ENABLE_TRIE_OPTIMISATION &&
+                        OP( startbranch ) == BRANCH )
+                {
+               /* demq.
+
+                   Assuming this was/is a branch we are dealing with: 'scan'
+                   now points at the item that follows the branch sequence,
+                   whatever it is. We now start at the beginning of the
+                   sequence and look for subsequences of
+
+                  BRANCH->EXACT=>x1
+                  BRANCH->EXACT=>x2
+                  tail
+
+                   which would be constructed from a pattern like
+                   /A|LIST|OF|WORDS/
+
+                  If we can find such a subsequence we need to turn the first
+                  element into a trie and then add the subsequent branch exact
+                  strings to the trie.
+
+                  We have two cases
+
+                     1. patterns where the whole set of branches can be
+                        converted.
+
+                    2. patterns where only a subset can be converted.
+
+                  In case 1 we can replace the whole set with a single regop
+                  for the trie. In case 2 we need to keep the start and end
+                  branches so
+
+                    'BRANCH EXACT; BRANCH EXACT; BRANCH X'
+                    becomes BRANCH TRIE; BRANCH X;
+
+                 There is an additional case, that being where there is a
+                 common prefix, which gets split out into an EXACT like node
+                 preceding the TRIE node.
+
+                 If x(1..n)==tail then we can do a simple trie, if not we make
+                 a "jump" trie, such that when we match the appropriate word
+                 we "jump" to the appropriate tail node. Essentially we turn
+                 a nested if into a case structure of sorts.
+
+               */
+
+                   int made=0;
+                   if (!re_trie_maxbuff) {
+                       re_trie_maxbuff = get_sv(RE_TRIE_MAXBUF_NAME, 1);
+                       if (!SvIOK(re_trie_maxbuff))
+                           sv_setiv(re_trie_maxbuff, RE_TRIE_MAXBUF_INIT);
+                   }
+                    if ( SvIV(re_trie_maxbuff)>=0  ) {
+                        regnode *cur;
+                        regnode *first = (regnode *)NULL;
+                        regnode *last = (regnode *)NULL;
+                        regnode *tail = scan;
+                        U8 trietype = 0;
+                        U32 count=0;
+
+#ifdef DEBUGGING
+                        SV * const mysv = sv_newmortal();   /* for dumping */
+#endif
+                        /* var tail is used because there may be a TAIL
+                           regop in the way. Ie, the exacts will point to the
+                           thing following the TAIL, but the last branch will
+                           point at the TAIL. So we advance tail. If we
+                           have nested (?:) we may have to move through several
+                           tails.
+                         */
+
+                        while ( OP( tail ) == TAIL ) {
+                            /* this is the TAIL generated by (?:) */
+                            tail = regnext( tail );
+                        }
+
+
+                        DEBUG_TRIE_COMPILE_r({
+                            regprop(RExC_rx, mysv, tail, NULL);
+                            PerlIO_printf( Perl_debug_log, "%*s%s%s\n",
+                              (int)depth * 2 + 2, "",
+                              "Looking for TRIE'able sequences. Tail node is: ",
+                              SvPV_nolen_const( mysv )
+                            );
+                        });
+
+                        /*
+
+                            Step through the branches
+                                cur represents each branch,
+                                noper is the first thing to be matched as part
+                                      of that branch
+                                noper_next is the regnext() of that node.
+
+                            We normally handle a case like this
+                            /FOO[xyz]|BAR[pqr]/ via a "jump trie" but we also
+                            support building with NOJUMPTRIE, which restricts
+                            the trie logic to structures like /FOO|BAR/.
+
+                            If noper is a trieable nodetype then the branch is
+                            a possible optimization target. If we are building
+                            under NOJUMPTRIE then we require that noper_next is
+                            the same as scan (our current position in the regex
+                            program).
+
+                            Once we have two or more consecutive such branches
+                            we can create a trie of the EXACT's contents and
+                            stitch it in place into the program.
+
+                            If the sequence represents all of the branches in
+                            the alternation we replace the entire thing with a
+                            single TRIE node.
+
+                            Otherwise when it is a subsequence we need to
+                            stitch it in place and replace only the relevant
+                            branches. This means the first branch has to remain
+                            as it is used by the alternation logic, and its
+                            next pointer, and needs to be repointed at the item
+                            on the branch chain following the last branch we
+                            have optimized away.
+
+                            This could be either a BRANCH, in which case the
+                            subsequence is internal, or it could be the item
+                            following the branch sequence in which case the
+                            subsequence is at the end (which does not
+                            necessarily mean the first node is the start of the
+                            alternation).
+
+                            TRIE_TYPE(X) is a define which maps the optype to a
+                            trietype.
+
+                                optype          |  trietype
+                                ----------------+-----------
+                                NOTHING         | NOTHING
+                                EXACT           | EXACT
+                                EXACTFU         | EXACTFU
+                                EXACTFU_SS      | EXACTFU
+                                EXACTFA         | EXACTFA
+
+
+                        */
+#define TRIE_TYPE(X) ( ( NOTHING == (X) ) ? NOTHING :   \
+                       ( EXACT == (X) )   ? EXACT :        \
+                       ( EXACTFU == (X) || EXACTFU_SS == (X) ) ? EXACTFU :        \
+                       ( EXACTFA == (X) ) ? EXACTFA :        \
+                       0 )
+
+                        /* dont use tail as the end marker for this traverse */
+                        for ( cur = startbranch ; cur != scan ; cur = regnext( cur ) ) {
+                            regnode * const noper = NEXTOPER( cur );
+                            U8 noper_type = OP( noper );
+                            U8 noper_trietype = TRIE_TYPE( noper_type );
+#if defined(DEBUGGING) || defined(NOJUMPTRIE)
+                            regnode * const noper_next = regnext( noper );
+                           U8 noper_next_type = (noper_next && noper_next != tail) ? OP(noper_next) : 0;
+                           U8 noper_next_trietype = (noper_next && noper_next != tail) ? TRIE_TYPE( noper_next_type ) :0;
+#endif
+
+                            DEBUG_TRIE_COMPILE_r({
+                                regprop(RExC_rx, mysv, cur, NULL);
+                                PerlIO_printf( Perl_debug_log, "%*s- %s (%d)",
+                                   (int)depth * 2 + 2,"", SvPV_nolen_const( mysv ), REG_NODE_NUM(cur) );
+
+                                regprop(RExC_rx, mysv, noper, NULL);
+                                PerlIO_printf( Perl_debug_log, " -> %s",
+                                    SvPV_nolen_const(mysv));
+
+                                if ( noper_next ) {
+                                  regprop(RExC_rx, mysv, noper_next, NULL);
+                                  PerlIO_printf( Perl_debug_log,"\t=> %s\t",
+                                    SvPV_nolen_const(mysv));
+                                }
+                                PerlIO_printf( Perl_debug_log, "(First==%d,Last==%d,Cur==%d,tt==%s,nt==%s,nnt==%s)\n",
+                                   REG_NODE_NUM(first), REG_NODE_NUM(last), REG_NODE_NUM(cur),
+                                  PL_reg_name[trietype], PL_reg_name[noper_trietype], PL_reg_name[noper_next_trietype]
+                               );
+                            });
+
+                            /* Is noper a trieable nodetype that can be merged
+                             * with the current trie (if there is one)? */
+                            if ( noper_trietype
+                                  &&
+                                  (
+                                        ( noper_trietype == NOTHING)
+                                        || ( trietype == NOTHING )
+                                        || ( trietype == noper_trietype )
+                                  )
+#ifdef NOJUMPTRIE
+                                  && noper_next == tail
+#endif
+                                  && count < U16_MAX)
+                            {
+                                /* Handle mergable triable node Either we are
+                                 * the first node in a new trieable sequence,
+                                 * in which case we do some bookkeeping,
+                                 * otherwise we update the end pointer. */
+                                if ( !first ) {
+                                    first = cur;
+                                   if ( noper_trietype == NOTHING ) {
+#if !defined(DEBUGGING) && !defined(NOJUMPTRIE)
+                                       regnode * const noper_next = regnext( noper );
+                                        U8 noper_next_type = (noper_next && noper_next!=tail) ? OP(noper_next) : 0;
+                                       U8 noper_next_trietype = noper_next_type ? TRIE_TYPE( noper_next_type ) :0;
+#endif
+
+                                        if ( noper_next_trietype ) {
+                                           trietype = noper_next_trietype;
+                                        } else if (noper_next_type)  {
+                                            /* a NOTHING regop is 1 regop wide.
+                                             * We need at least two for a trie
+                                             * so we can't merge this in */
+                                            first = NULL;
+                                        }
+                                    } else {
+                                        trietype = noper_trietype;
+                                    }
+                                } else {
+                                    if ( trietype == NOTHING )
+                                        trietype = noper_trietype;
+                                    last = cur;
+                                }
+                               if (first)
+                                   count++;
+                            } /* end handle mergable triable node */
+                            else {
+                                /* handle unmergable node -
+                                 * noper may either be a triable node which can
+                                 * not be tried together with the current trie,
+                                 * or a non triable node */
+                                if ( last ) {
+                                    /* If last is set and trietype is not
+                                     * NOTHING then we have found at least two
+                                     * triable branch sequences in a row of a
+                                     * similar trietype so we can turn them
+                                     * into a trie. If/when we allow NOTHING to
+                                     * start a trie sequence this condition
+                                     * will be required, and it isn't expensive
+                                     * so we leave it in for now. */
+                                    if ( trietype && trietype != NOTHING )
+                                        make_trie( pRExC_state,
+                                                startbranch, first, cur, tail,
+                                                count, trietype, depth+1 );
+                                    last = NULL; /* note: we clear/update
+                                                    first, trietype etc below,
+                                                    so we dont do it here */
+                                }
+                                if ( noper_trietype
+#ifdef NOJUMPTRIE
+                                     && noper_next == tail
+#endif
+                                ){
+                                    /* noper is triable, so we can start a new
+                                     * trie sequence */
+                                    count = 1;
+                                    first = cur;
+                                    trietype = noper_trietype;
+                                } else if (first) {
+                                    /* if we already saw a first but the
+                                     * current node is not triable then we have
+                                     * to reset the first information. */
+                                    count = 0;
+                                    first = NULL;
+                                    trietype = 0;
+                                }
+                            } /* end handle unmergable node */
+                        } /* loop over branches */
+                        DEBUG_TRIE_COMPILE_r({
+                            regprop(RExC_rx, mysv, cur, NULL);
+                            PerlIO_printf( Perl_debug_log,
+                              "%*s- %s (%d) <SCAN FINISHED>\n",
+                              (int)depth * 2 + 2,
+                              "", SvPV_nolen_const( mysv ),REG_NODE_NUM(cur));
+
+                        });
+                        if ( last && trietype ) {
+                            if ( trietype != NOTHING ) {
+                                /* the last branch of the sequence was part of
+                                 * a trie, so we have to construct it here
+                                 * outside of the loop */
+                                made= make_trie( pRExC_state, startbranch,
+                                                 first, scan, tail, count,
+                                                 trietype, depth+1 );
+#ifdef TRIE_STUDY_OPT
+                                if ( ((made == MADE_EXACT_TRIE &&
+                                     startbranch == first)
+                                     || ( first_non_open == first )) &&
+                                     depth==0 ) {
+                                    flags |= SCF_TRIE_RESTUDY;
+                                    if ( startbranch == first
+                                         && scan == tail )
+                                    {
+                                        RExC_seen &=~REG_TOP_LEVEL_BRANCHES_SEEN;
+                                    }
+                                }
+#endif
+                            } else {
+                                /* at this point we know whatever we have is a
+                                 * NOTHING sequence/branch AND if 'startbranch'
+                                 * is 'first' then we can turn the whole thing
+                                 * into a NOTHING
+                                 */
+                                if ( startbranch == first ) {
+                                    regnode *opt;
+                                    /* the entire thing is a NOTHING sequence,
+                                     * something like this: (?:|) So we can
+                                     * turn it into a plain NOTHING op. */
+                                    DEBUG_TRIE_COMPILE_r({
+                                        regprop(RExC_rx, mysv, cur, NULL);
+                                        PerlIO_printf( Perl_debug_log,
+                                          "%*s- %s (%d) <NOTHING BRANCH SEQUENCE>\n", (int)depth * 2 + 2,
+                                          "", SvPV_nolen_const( mysv ),REG_NODE_NUM(cur));
+
+                                    });
+                                    OP(startbranch)= NOTHING;
+                                    NEXT_OFF(startbranch)= tail - startbranch;
+                                    for ( opt= startbranch + 1; opt < tail ; opt++ )
+                                        OP(opt)= OPTIMIZED;
+                                }
+                            }
+                        } /* end if ( last) */
+                    } /* TRIE_MAXBUF is non zero */
+
+                } /* do trie */
+
+           }
+           else if ( code == BRANCHJ ) {  /* single branch is optimized. */
+               scan = NEXTOPER(NEXTOPER(scan));
+           } else                      /* single branch is optimized. */
+               scan = NEXTOPER(scan);
+           continue;
+       } else if (OP(scan) == SUSPEND || OP(scan) == GOSUB || OP(scan) == GOSTART) {
+           scan_frame *newframe = NULL;
+           I32 paren;
+           regnode *start;
+           regnode *end;
+            U32 my_recursed_depth= recursed_depth;
+
+           if (OP(scan) != SUSPEND) {
+                /* set the pointer */
+               if (OP(scan) == GOSUB) {
+                   paren = ARG(scan);
+                   RExC_recurse[ARG2L(scan)] = scan;
+                    start = RExC_open_parens[paren-1];
+                    end   = RExC_close_parens[paren-1];
+                } else {
+                    paren = 0;
+                    start = RExC_rxi->program + 1;
+                    end   = RExC_opend;
+                }
+                if (!recursed_depth
+                    ||
+                    !PAREN_TEST(RExC_study_chunk_recursed + ((recursed_depth-1) * RExC_study_chunk_recursed_bytes), paren)
+                ) {
+                    if (!recursed_depth) {
+                        Zero(RExC_study_chunk_recursed, RExC_study_chunk_recursed_bytes, U8);
+                    } else {
+                        Copy(RExC_study_chunk_recursed + ((recursed_depth-1) * RExC_study_chunk_recursed_bytes),
+                             RExC_study_chunk_recursed + (recursed_depth * RExC_study_chunk_recursed_bytes),
+                             RExC_study_chunk_recursed_bytes, U8);
+                    }
+                    /* we havent recursed into this paren yet, so recurse into it */
+                   DEBUG_STUDYDATA("set:", data,depth);
+                    PAREN_SET(RExC_study_chunk_recursed + (recursed_depth * RExC_study_chunk_recursed_bytes), paren);
+                    my_recursed_depth= recursed_depth + 1;
+                    Newx(newframe,1,scan_frame);
+                } else {
+                   DEBUG_STUDYDATA("inf:", data,depth);
+                    /* some form of infinite recursion, assume infinite length
+                     * */
+                    if (flags & SCF_DO_SUBSTR) {
+                        scan_commit(pRExC_state, data, minlenp, is_inf);
+                        data->longest = &(data->longest_float);
+                    }
+                    is_inf = is_inf_internal = 1;
+                    if (flags & SCF_DO_STCLASS_OR) /* Allow everything */
+                        ssc_anything(data->start_class);
+                    flags &= ~SCF_DO_STCLASS;
+               }
+            } else {
+               Newx(newframe,1,scan_frame);
+               paren = stopparen;
+               start = scan+2;
+               end = regnext(scan);
+           }
+           if (newframe) {
+                assert(start);
+                assert(end);
+               SAVEFREEPV(newframe);
+               newframe->next = regnext(scan);
+               newframe->last = last;
+               newframe->stop = stopparen;
+               newframe->prev = frame;
+                newframe->prev_recursed_depth = recursed_depth;
+
+                DEBUG_STUDYDATA("frame-new:",data,depth);
+                DEBUG_PEEP("fnew", scan, depth);
+
+               frame = newframe;
+               scan =  start;
+               stopparen = paren;
+               last = end;
+                depth = depth + 1;
+                recursed_depth= my_recursed_depth;
+
+               continue;
+           }
+       }
+       else if (OP(scan) == EXACT) {
+           SSize_t l = STR_LEN(scan);
+           UV uc;
+           if (UTF) {
+               const U8 * const s = (U8*)STRING(scan);
+               uc = utf8_to_uvchr_buf(s, s + l, NULL);
+               l = utf8_length(s, s + l);
+           } else {
+               uc = *((U8*)STRING(scan));
+           }
+           min += l;
+           if (flags & SCF_DO_SUBSTR) { /* Update longest substr. */
+               /* The code below prefers earlier match for fixed
+                  offset, later match for variable offset.  */
+               if (data->last_end == -1) { /* Update the start info. */
+                   data->last_start_min = data->pos_min;
+                   data->last_start_max = is_inf
+                       ? SSize_t_MAX : data->pos_min + data->pos_delta;
+               }
+               sv_catpvn(data->last_found, STRING(scan), STR_LEN(scan));
+               if (UTF)
+                   SvUTF8_on(data->last_found);
+               {
+                   SV * const sv = data->last_found;
+                   MAGIC * const mg = SvUTF8(sv) && SvMAGICAL(sv) ?
+                       mg_find(sv, PERL_MAGIC_utf8) : NULL;
+                   if (mg && mg->mg_len >= 0)
+                       mg->mg_len += utf8_length((U8*)STRING(scan),
+                                              (U8*)STRING(scan)+STR_LEN(scan));
+               }
+               data->last_end = data->pos_min + l;
+               data->pos_min += l; /* As in the first entry. */
+               data->flags &= ~SF_BEFORE_EOL;
+           }
+
+            /* ANDing the code point leaves at most it, and not in locale, and
+             * can't match null string */
+           if (flags & SCF_DO_STCLASS_AND) {
+                ssc_cp_and(data->start_class, uc);
+                ANYOF_FLAGS(data->start_class) &= ~ANYOF_EMPTY_STRING;
+                ssc_clear_locale(data->start_class);
+           }
+           else if (flags & SCF_DO_STCLASS_OR) {
+                ssc_add_cp(data->start_class, uc);
+               ssc_and(pRExC_state, data->start_class, (regnode_charclass *) and_withp);
+
+                /* See commit msg 749e076fceedeb708a624933726e7989f2302f6a */
+                ANYOF_FLAGS(data->start_class) &= ~ANYOF_EMPTY_STRING;
+           }
+           flags &= ~SCF_DO_STCLASS;
+       }
+       else if (PL_regkind[OP(scan)] == EXACT) { /* But OP != EXACT! */
+           SSize_t l = STR_LEN(scan);
+           UV uc = *((U8*)STRING(scan));
+            SV* EXACTF_invlist = _new_invlist(4); /* Start out big enough for 2
+                                                     separate code points */
+
+           /* Search for fixed substrings supports EXACT only. */
+           if (flags & SCF_DO_SUBSTR) {
+               assert(data);
+                scan_commit(pRExC_state, data, minlenp, is_inf);
+           }
+           if (UTF) {
+               const U8 * const s = (U8 *)STRING(scan);
+               uc = utf8_to_uvchr_buf(s, s + l, NULL);
+               l = utf8_length(s, s + l);
+           }
+           if (unfolded_multi_char) {
+                RExC_seen |= REG_UNFOLDED_MULTI_SEEN;
+           }
+           min += l - min_subtract;
+            assert (min >= 0);
+            delta += min_subtract;
+           if (flags & SCF_DO_SUBSTR) {
+               data->pos_min += l - min_subtract;
+               if (data->pos_min < 0) {
+                    data->pos_min = 0;
+                }
+                data->pos_delta += min_subtract;
+               if (min_subtract) {
+                   data->longest = &(data->longest_float);
+               }
+           }
+            if (OP(scan) == EXACTFL) {
+
+                /* We don't know what the folds are; it could be anything. XXX
+                 * Actually, we only support UTF-8 encoding for code points
+                 * above Latin1, so we could know what those folds are. */
+                EXACTF_invlist = _add_range_to_invlist(EXACTF_invlist,
+                                                       0,
+                                                       UV_MAX);
+            }
+            else {  /* Non-locale EXACTFish */
+                EXACTF_invlist = add_cp_to_invlist(EXACTF_invlist, uc);
+                if (flags & SCF_DO_STCLASS_AND) {
+                    ssc_clear_locale(data->start_class);
+                }
+                if (uc < 256) { /* We know what the Latin1 folds are ... */
+                    if (IS_IN_SOME_FOLD_L1(uc)) {   /* For instance, we
+                                                       know if anything folds
+                                                       with this */
+                        EXACTF_invlist = add_cp_to_invlist(EXACTF_invlist,
+                                                           PL_fold_latin1[uc]);
+                        if (OP(scan) != EXACTFA) { /* The folds below aren't
+                                                      legal under /iaa */
+                            if (isARG2_lower_or_UPPER_ARG1('s', uc)) {
+                                EXACTF_invlist
+                                    = add_cp_to_invlist(EXACTF_invlist,
+                                                LATIN_SMALL_LETTER_SHARP_S);
+                            }
+                            else if (uc == LATIN_SMALL_LETTER_SHARP_S) {
+                                EXACTF_invlist
+                                    = add_cp_to_invlist(EXACTF_invlist, 's');
+                                EXACTF_invlist
+                                    = add_cp_to_invlist(EXACTF_invlist, 'S');
+                            }
+                        }
+
+                        /* We also know if there are above-Latin1 code points
+                         * that fold to this (none legal for ASCII and /iaa) */
+                        if ((! isASCII(uc) || OP(scan) != EXACTFA)
+                            && HAS_NONLATIN1_FOLD_CLOSURE(uc))
+                        {
+                            /* XXX We could know exactly what does fold to this
+                             * if the reverse folds are loaded, as currently in
+                             * S_regclass() */
+                            _invlist_union(EXACTF_invlist,
+                                           PL_AboveLatin1,
+                                           &EXACTF_invlist);
+                        }
+                    }
+                }
+                else {  /* Non-locale, above Latin1.  XXX We don't currently
+                           know what participates in folds with this, so have
+                           to assume anything could */
+
+                    /* XXX We could know exactly what does fold to this if the
+                     * reverse folds are loaded, as currently in S_regclass().
+                     * But we do know that under /iaa nothing in the ASCII
+                     * range can participate */
+                    if (OP(scan) == EXACTFA) {
+                        _invlist_union_complement_2nd(EXACTF_invlist,
+                                                      PL_XPosix_ptrs[_CC_ASCII],
+                                                      &EXACTF_invlist);
+                    }
+                    else {
+                        EXACTF_invlist = _add_range_to_invlist(EXACTF_invlist,
+                                                               0, UV_MAX);
+                    }
+                }
+            }
+           if (flags & SCF_DO_STCLASS_AND) {
+                ANYOF_FLAGS(data->start_class) &= ~ANYOF_EMPTY_STRING;
+                ANYOF_POSIXL_ZERO(data->start_class);
+                ssc_intersection(data->start_class, EXACTF_invlist, FALSE);
+           }
+           else if (flags & SCF_DO_STCLASS_OR) {
+                ssc_union(data->start_class, EXACTF_invlist, FALSE);
+               ssc_and(pRExC_state, data->start_class, (regnode_charclass *) and_withp);
+
+                /* See commit msg 749e076fceedeb708a624933726e7989f2302f6a */
+                ANYOF_FLAGS(data->start_class) &= ~ANYOF_EMPTY_STRING;
+           }
+           flags &= ~SCF_DO_STCLASS;
+            SvREFCNT_dec(EXACTF_invlist);
+       }
+       else if (REGNODE_VARIES(OP(scan))) {
+           SSize_t mincount, maxcount, minnext, deltanext, pos_before = 0;
+           I32 fl = 0, f = flags;
+           regnode * const oscan = scan;
+           regnode_ssc this_class;
+           regnode_ssc *oclass = NULL;
+           I32 next_is_eval = 0;
+
+           switch (PL_regkind[OP(scan)]) {
+           case WHILEM:                /* End of (?:...)* . */
+               scan = NEXTOPER(scan);
+               goto finish;
+           case PLUS:
+               if (flags & (SCF_DO_SUBSTR | SCF_DO_STCLASS)) {
+                   next = NEXTOPER(scan);
+                   if (OP(next) == EXACT || (flags & SCF_DO_STCLASS)) {
+                       mincount = 1;
+                       maxcount = REG_INFTY;
+                       next = regnext(scan);
+                       scan = NEXTOPER(scan);
+                       goto do_curly;
+                   }
+               }
+               if (flags & SCF_DO_SUBSTR)
+                   data->pos_min++;
+               min++;
+               /* Fall through. */
+           case STAR:
+               if (flags & SCF_DO_STCLASS) {
+                   mincount = 0;
+                   maxcount = REG_INFTY;
+                   next = regnext(scan);
+                   scan = NEXTOPER(scan);
+                   goto do_curly;
+               }
+               if (flags & SCF_DO_SUBSTR) {
+                    scan_commit(pRExC_state, data, minlenp, is_inf);
+                    /* Cannot extend fixed substrings */
+                   data->longest = &(data->longest_float);
+               }
+                is_inf = is_inf_internal = 1;
+                scan = regnext(scan);
+               goto optimize_curly_tail;
+           case CURLY:
+               if (stopparen>0 && (OP(scan)==CURLYN || OP(scan)==CURLYM)
+                   && (scan->flags == stopparen))
+               {
+                   mincount = 1;
+                   maxcount = 1;
+               } else {
+                   mincount = ARG1(scan);
+                   maxcount = ARG2(scan);
+               }
+               next = regnext(scan);
+               if (OP(scan) == CURLYX) {
+                   I32 lp = (data ? *(data->last_closep) : 0);
+                   scan->flags = ((lp <= (I32)U8_MAX) ? (U8)lp : U8_MAX);
+               }
+               scan = NEXTOPER(scan) + EXTRA_STEP_2ARGS;
+               next_is_eval = (OP(scan) == EVAL);
+             do_curly:
+               if (flags & SCF_DO_SUBSTR) {
+                    if (mincount == 0)
+                        scan_commit(pRExC_state, data, minlenp, is_inf);
+                    /* Cannot extend fixed substrings */
+                   pos_before = data->pos_min;
+               }
+               if (data) {
+                   fl = data->flags;
+                   data->flags &= ~(SF_HAS_PAR|SF_IN_PAR|SF_HAS_EVAL);
+                   if (is_inf)
+                       data->flags |= SF_IS_INF;
+               }
+               if (flags & SCF_DO_STCLASS) {
+                   ssc_init(pRExC_state, &this_class);
+                   oclass = data->start_class;
+                   data->start_class = &this_class;
+                   f |= SCF_DO_STCLASS_AND;
+                   f &= ~SCF_DO_STCLASS_OR;
+               }
+               /* Exclude from super-linear cache processing any {n,m}
+                  regops for which the combination of input pos and regex
+                  pos is not enough information to determine if a match
+                  will be possible.
+
+                  For example, in the regex /foo(bar\s*){4,8}baz/ with the
+                  regex pos at the \s*, the prospects for a match depend not
+                  only on the input position but also on how many (bar\s*)
+                  repeats into the {4,8} we are. */
+               if ((mincount > 1) || (maxcount > 1 && maxcount != REG_INFTY))
+                   f &= ~SCF_WHILEM_VISITED_POS;
+
+               /* This will finish on WHILEM, setting scan, or on NULL: */
+               minnext = study_chunk(pRExC_state, &scan, minlenp, &deltanext,
+                                  last, data, stopparen, recursed_depth, NULL,
+                                  (mincount == 0
+                                   ? (f & ~SCF_DO_SUBSTR)
+                                   : f)
+                                  ,depth+1);
+
+               if (flags & SCF_DO_STCLASS)
+                   data->start_class = oclass;
+               if (mincount == 0 || minnext == 0) {
+                   if (flags & SCF_DO_STCLASS_OR) {
+                       ssc_or(pRExC_state, data->start_class, (regnode_charclass *) &this_class);
+                   }
+                   else if (flags & SCF_DO_STCLASS_AND) {
+                       /* Switch to OR mode: cache the old value of
+                        * data->start_class */
+                       INIT_AND_WITHP;
+                       StructCopy(data->start_class, and_withp, regnode_ssc);
+                       flags &= ~SCF_DO_STCLASS_AND;
+                       StructCopy(&this_class, data->start_class, regnode_ssc);
+                       flags |= SCF_DO_STCLASS_OR;
+                        ANYOF_FLAGS(data->start_class) |= ANYOF_EMPTY_STRING;
+                   }
+               } else {                /* Non-zero len */
+                   if (flags & SCF_DO_STCLASS_OR) {
+                       ssc_or(pRExC_state, data->start_class, (regnode_charclass *) &this_class);
+                       ssc_and(pRExC_state, data->start_class, (regnode_charclass *) and_withp);
+                   }
+                   else if (flags & SCF_DO_STCLASS_AND)
+                       ssc_and(pRExC_state, data->start_class, (regnode_charclass *) &this_class);
+                   flags &= ~SCF_DO_STCLASS;
+               }
+               if (!scan)              /* It was not CURLYX, but CURLY. */
+                   scan = next;
+               if (!(flags & SCF_TRIE_DOING_RESTUDY)
+                   /* ? quantifier ok, except for (?{ ... }) */
+                   && (next_is_eval || !(mincount == 0 && maxcount == 1))
+                   && (minnext == 0) && (deltanext == 0)
+                   && data && !(data->flags & (SF_HAS_PAR|SF_IN_PAR))
+                    && maxcount <= REG_INFTY/3) /* Complement check for big
+                                                   count */
+               {
+                   /* Fatal warnings may leak the regexp without this: */
+                   SAVEFREESV(RExC_rx_sv);
+                   ckWARNreg(RExC_parse,
+                           "Quantifier unexpected on zero-length expression");
+                   (void)ReREFCNT_inc(RExC_rx_sv);
+               }
+
+               min += minnext * mincount;
+               is_inf_internal |= deltanext == SSize_t_MAX
+                         || (maxcount == REG_INFTY && minnext + deltanext > 0);
+               is_inf |= is_inf_internal;
+                if (is_inf) {
+                   delta = SSize_t_MAX;
+                } else {
+                   delta += (minnext + deltanext) * maxcount
+                             - minnext * mincount;
+                }
+               /* Try powerful optimization CURLYX => CURLYN. */
+               if (  OP(oscan) == CURLYX && data
+                     && data->flags & SF_IN_PAR
+                     && !(data->flags & SF_HAS_EVAL)
+                     && !deltanext && minnext == 1 ) {
+                   /* Try to optimize to CURLYN.  */
+                   regnode *nxt = NEXTOPER(oscan) + EXTRA_STEP_2ARGS;
+                   regnode * const nxt1 = nxt;
+#ifdef DEBUGGING
+                   regnode *nxt2;
+#endif
+
+                   /* Skip open. */
+                   nxt = regnext(nxt);
+                   if (!REGNODE_SIMPLE(OP(nxt))
+                       && !(PL_regkind[OP(nxt)] == EXACT
+                            && STR_LEN(nxt) == 1))
+                       goto nogo;
+#ifdef DEBUGGING
+                   nxt2 = nxt;
+#endif
+                   nxt = regnext(nxt);
+                   if (OP(nxt) != CLOSE)
+                       goto nogo;
+                   if (RExC_open_parens) {
+                       RExC_open_parens[ARG(nxt1)-1]=oscan; /*open->CURLYM*/
+                       RExC_close_parens[ARG(nxt1)-1]=nxt+2; /*close->while*/
+                   }
+                   /* Now we know that nxt2 is the only contents: */
+                   oscan->flags = (U8)ARG(nxt);
+                   OP(oscan) = CURLYN;
+                   OP(nxt1) = NOTHING; /* was OPEN. */
+
+#ifdef DEBUGGING
+                   OP(nxt1 + 1) = OPTIMIZED; /* was count. */
+                   NEXT_OFF(nxt1+ 1) = 0; /* just for consistency. */
+                   NEXT_OFF(nxt2) = 0; /* just for consistency with CURLY. */
+                   OP(nxt) = OPTIMIZED;        /* was CLOSE. */
+                   OP(nxt + 1) = OPTIMIZED; /* was count. */
+                   NEXT_OFF(nxt+ 1) = 0; /* just for consistency. */
+#endif
+               }
+             nogo:
+
+               /* Try optimization CURLYX => CURLYM. */
+               if (  OP(oscan) == CURLYX && data
+                     && !(data->flags & SF_HAS_PAR)
+                     && !(data->flags & SF_HAS_EVAL)
+                     && !deltanext     /* atom is fixed width */
+                     && minnext != 0   /* CURLYM can't handle zero width */
+
+                         /* Nor characters whose fold at run-time may be
+                          * multi-character */
+                      && ! (RExC_seen & REG_UNFOLDED_MULTI_SEEN)
+               ) {
+                   /* XXXX How to optimize if data == 0? */
+                   /* Optimize to a simpler form.  */
+                   regnode *nxt = NEXTOPER(oscan) + EXTRA_STEP_2ARGS; /* OPEN */
+                   regnode *nxt2;
+
+                   OP(oscan) = CURLYM;
+                   while ( (nxt2 = regnext(nxt)) /* skip over embedded stuff*/
+                           && (OP(nxt2) != WHILEM))
+                       nxt = nxt2;
+                   OP(nxt2)  = SUCCEED; /* Whas WHILEM */
+                   /* Need to optimize away parenths. */
+                   if ((data->flags & SF_IN_PAR) && OP(nxt) == CLOSE) {
+                       /* Set the parenth number.  */
+                       regnode *nxt1 = NEXTOPER(oscan) + EXTRA_STEP_2ARGS; /* OPEN*/
+
+                       oscan->flags = (U8)ARG(nxt);
+                       if (RExC_open_parens) {
+                           RExC_open_parens[ARG(nxt1)-1]=oscan; /*open->CURLYM*/
+                           RExC_close_parens[ARG(nxt1)-1]=nxt2+1; /*close->NOTHING*/
+                       }
+                       OP(nxt1) = OPTIMIZED;   /* was OPEN. */
+                       OP(nxt) = OPTIMIZED;    /* was CLOSE. */
+
+#ifdef DEBUGGING
+                       OP(nxt1 + 1) = OPTIMIZED; /* was count. */
+                       OP(nxt + 1) = OPTIMIZED; /* was count. */
+                       NEXT_OFF(nxt1 + 1) = 0; /* just for consistency. */
+                       NEXT_OFF(nxt + 1) = 0; /* just for consistency. */
+#endif
+#if 0
+                       while ( nxt1 && (OP(nxt1) != WHILEM)) {
+                           regnode *nnxt = regnext(nxt1);
+                           if (nnxt == nxt) {
+                               if (reg_off_by_arg[OP(nxt1)])
+                                   ARG_SET(nxt1, nxt2 - nxt1);
+                               else if (nxt2 - nxt1 < U16_MAX)
+                                   NEXT_OFF(nxt1) = nxt2 - nxt1;
+                               else
+                                   OP(nxt) = NOTHING;  /* Cannot beautify */
+                           }
+                           nxt1 = nnxt;
+                       }
+#endif
+                       /* Optimize again: */
+                       study_chunk(pRExC_state, &nxt1, minlenp, &deltanext, nxt,
+                                    NULL, stopparen, recursed_depth, NULL, 0,depth+1);
+                   }
+                   else
+                       oscan->flags = 0;
+               }
+               else if ((OP(oscan) == CURLYX)
+                        && (flags & SCF_WHILEM_VISITED_POS)
+                        /* See the comment on a similar expression above.
+                           However, this time it's not a subexpression
+                           we care about, but the expression itself. */
+                        && (maxcount == REG_INFTY)
+                        && data && ++data->whilem_c < 16) {
+                   /* This stays as CURLYX, we can put the count/of pair. */
+                   /* Find WHILEM (as in regexec.c) */
+                   regnode *nxt = oscan + NEXT_OFF(oscan);
+
+                   if (OP(PREVOPER(nxt)) == NOTHING) /* LONGJMP */
+                       nxt += ARG(nxt);
+                   PREVOPER(nxt)->flags = (U8)(data->whilem_c
+                       | (RExC_whilem_seen << 4)); /* On WHILEM */
+               }
+               if (data && fl & (SF_HAS_PAR|SF_IN_PAR))
+                   pars++;
+               if (flags & SCF_DO_SUBSTR) {
+                   SV *last_str = NULL;
+                    STRLEN last_chrs = 0;
+                   int counted = mincount != 0;
+
+                    if (data->last_end > 0 && mincount != 0) { /* Ends with a
+                                                                  string. */
+                       SSize_t b = pos_before >= data->last_start_min
+                           ? pos_before : data->last_start_min;
+                       STRLEN l;
+                       const char * const s = SvPV_const(data->last_found, l);
+                       SSize_t old = b - data->last_start_min;
+
+                       if (UTF)
+                           old = utf8_hop((U8*)s, old) - (U8*)s;
+                       l -= old;
+                       /* Get the added string: */
+                       last_str = newSVpvn_utf8(s  + old, l, UTF);
+                        last_chrs = UTF ? utf8_length((U8*)(s + old),
+                                            (U8*)(s + old + l)) : l;
+                       if (deltanext == 0 && pos_before == b) {
+                           /* What was added is a constant string */
+                           if (mincount > 1) {
+
+                               SvGROW(last_str, (mincount * l) + 1);
+                               repeatcpy(SvPVX(last_str) + l,
+                                         SvPVX_const(last_str), l,
+                                          mincount - 1);
+                               SvCUR_set(last_str, SvCUR(last_str) * mincount);
+                               /* Add additional parts. */
+                               SvCUR_set(data->last_found,
+                                         SvCUR(data->last_found) - l);
+                               sv_catsv(data->last_found, last_str);
+                               {
+                                   SV * sv = data->last_found;
+                                   MAGIC *mg =
+                                       SvUTF8(sv) && SvMAGICAL(sv) ?
+                                       mg_find(sv, PERL_MAGIC_utf8) : NULL;
+                                   if (mg && mg->mg_len >= 0)
+                                       mg->mg_len += last_chrs * (mincount-1);
+                               }
+                                last_chrs *= mincount;
+                               data->last_end += l * (mincount - 1);
+                           }
+                       } else {
+                           /* start offset must point into the last copy */
+                           data->last_start_min += minnext * (mincount - 1);
+                           data->last_start_max += is_inf ? SSize_t_MAX
+                               : (maxcount - 1) * (minnext + data->pos_delta);
+                       }
+                   }
+                   /* It is counted once already... */
+                   data->pos_min += minnext * (mincount - counted);
+#if 0
+PerlIO_printf(Perl_debug_log, "counted=%"UVdf" deltanext=%"UVdf
+                              " SSize_t_MAX=%"UVdf" minnext=%"UVdf
+                              " maxcount=%"UVdf" mincount=%"UVdf"\n",
+    (UV)counted, (UV)deltanext, (UV)SSize_t_MAX, (UV)minnext, (UV)maxcount,
+    (UV)mincount);
+if (deltanext != SSize_t_MAX)
+PerlIO_printf(Perl_debug_log, "LHS=%"UVdf" RHS=%"UVdf"\n",
+    (UV)(-counted * deltanext + (minnext + deltanext) * maxcount
+          - minnext * mincount), (UV)(SSize_t_MAX - data->pos_delta));
+#endif
+                   if (deltanext == SSize_t_MAX
+                        || -counted * deltanext + (minnext + deltanext) * maxcount - minnext * mincount >= SSize_t_MAX - data->pos_delta)
+                       data->pos_delta = SSize_t_MAX;
+                   else
+                       data->pos_delta += - counted * deltanext +
+                       (minnext + deltanext) * maxcount - minnext * mincount;
+                   if (mincount != maxcount) {
+                        /* Cannot extend fixed substrings found inside
+                           the group.  */
+                        scan_commit(pRExC_state, data, minlenp, is_inf);
+                       if (mincount && last_str) {
+                           SV * const sv = data->last_found;
+                           MAGIC * const mg = SvUTF8(sv) && SvMAGICAL(sv) ?
+                               mg_find(sv, PERL_MAGIC_utf8) : NULL;
+
+                           if (mg)
+                               mg->mg_len = -1;
+                           sv_setsv(sv, last_str);
+                           data->last_end = data->pos_min;
+                           data->last_start_min = data->pos_min - last_chrs;
+                           data->last_start_max = is_inf
+                               ? SSize_t_MAX
+                               : data->pos_min + data->pos_delta - last_chrs;
+                       }
+                       data->longest = &(data->longest_float);
+                   }
+                   SvREFCNT_dec(last_str);
+               }
+               if (data && (fl & SF_HAS_EVAL))
+                   data->flags |= SF_HAS_EVAL;
+             optimize_curly_tail:
+               if (OP(oscan) != CURLYX) {
+                   while (PL_regkind[OP(next = regnext(oscan))] == NOTHING
+                          && NEXT_OFF(next))
+                       NEXT_OFF(oscan) += NEXT_OFF(next);
+               }
+               continue;
+
+           default:
+#ifdef DEBUGGING
+                Perl_croak(aTHX_ "panic: unexpected varying REx opcode %d",
+                                                                    OP(scan));
+#endif
+            case REF:
+            case CLUMP:
+               if (flags & SCF_DO_SUBSTR) {
+                    /* Cannot expect anything... */
+                    scan_commit(pRExC_state, data, minlenp, is_inf);
+                   data->longest = &(data->longest_float);
+               }
+               is_inf = is_inf_internal = 1;
+               if (flags & SCF_DO_STCLASS_OR) {
+                    if (OP(scan) == CLUMP) {
+                        /* Actually is any start char, but very few code points
+                         * aren't start characters */
+                        ssc_match_all_cp(data->start_class);
+                    }
+                    else {
+                        ssc_anything(data->start_class);
+                    }
+                }
+               flags &= ~SCF_DO_STCLASS;
+               break;
+           }
+       }
+       else if (OP(scan) == LNBREAK) {
+           if (flags & SCF_DO_STCLASS) {
+               if (flags & SCF_DO_STCLASS_AND) {
+                    ssc_intersection(data->start_class,
+                                    PL_XPosix_ptrs[_CC_VERTSPACE], FALSE);
+                    ssc_clear_locale(data->start_class);
+                    ANYOF_FLAGS(data->start_class) &= ~ANYOF_EMPTY_STRING;
+                }
+                else if (flags & SCF_DO_STCLASS_OR) {
+                    ssc_union(data->start_class,
+                              PL_XPosix_ptrs[_CC_VERTSPACE],
+                              FALSE);
+                   ssc_and(pRExC_state, data->start_class, (regnode_charclass *) and_withp);
+
+                    /* See commit msg for
+                     * 749e076fceedeb708a624933726e7989f2302f6a */
+                    ANYOF_FLAGS(data->start_class) &= ~ANYOF_EMPTY_STRING;
+                }
+               flags &= ~SCF_DO_STCLASS;
+            }
+           min++;
+           delta++;    /* Because of the 2 char string cr-lf */
+            if (flags & SCF_DO_SUBSTR) {
+                /* Cannot expect anything... */
+                scan_commit(pRExC_state, data, minlenp, is_inf);
+               data->pos_min += 1;
+               data->pos_delta += 1;
+               data->longest = &(data->longest_float);
+           }
+       }
+       else if (REGNODE_SIMPLE(OP(scan))) {
+
+           if (flags & SCF_DO_SUBSTR) {
+                scan_commit(pRExC_state, data, minlenp, is_inf);
+               data->pos_min++;
+           }
+           min++;
+           if (flags & SCF_DO_STCLASS) {
+                bool invert = 0;
+                SV* my_invlist = NULL;
+                U8 namedclass;
+
+                /* See commit msg 749e076fceedeb708a624933726e7989f2302f6a */
+                ANYOF_FLAGS(data->start_class) &= ~ANYOF_EMPTY_STRING;
+
+               /* Some of the logic below assumes that switching
+                  locale on will only add false positives. */
+               switch (OP(scan)) {
+
+               default:
+#ifdef DEBUGGING
+                   Perl_croak(aTHX_ "panic: unexpected simple REx opcode %d",
+                                                                     OP(scan));
+#endif
+               case CANY:
+               case SANY:
+                   if (flags & SCF_DO_STCLASS_OR) /* Allow everything */
+                       ssc_match_all_cp(data->start_class);
+                   break;
+
+               case REG_ANY:
+                    {
+                        SV* REG_ANY_invlist = _new_invlist(2);
+                        REG_ANY_invlist = add_cp_to_invlist(REG_ANY_invlist,
+                                                            '\n');
+                        if (flags & SCF_DO_STCLASS_OR) {
+                            ssc_union(data->start_class,
+                                      REG_ANY_invlist,
+                                      TRUE /* TRUE => invert, hence all but \n
+                                            */
+                                      );
+                        }
+                        else if (flags & SCF_DO_STCLASS_AND) {
+                            ssc_intersection(data->start_class,
+                                             REG_ANY_invlist,
+                                             TRUE  /* TRUE => invert */
+                                             );
+                            ssc_clear_locale(data->start_class);
+                        }
+                        SvREFCNT_dec_NN(REG_ANY_invlist);
+                   }
+                   break;
+
+                case ANYOF:
+                   if (flags & SCF_DO_STCLASS_AND)
+                       ssc_and(pRExC_state, data->start_class,
+                                (regnode_charclass *) scan);
+                   else
+                       ssc_or(pRExC_state, data->start_class,
+                                                          (regnode_charclass *) scan);
+                   break;
+
+               case NPOSIXL:
+                    invert = 1;
+                    /* FALL THROUGH */
+
+               case POSIXL:
+                    namedclass = classnum_to_namedclass(FLAGS(scan)) + invert;
+                    if (flags & SCF_DO_STCLASS_AND) {
+                        bool was_there = cBOOL(
+                                          ANYOF_POSIXL_TEST(data->start_class,
+                                                                 namedclass));
+                        ANYOF_POSIXL_ZERO(data->start_class);
+                        if (was_there) {    /* Do an AND */
+                            ANYOF_POSIXL_SET(data->start_class, namedclass);
+                        }
+                        /* No individual code points can now match */
+                        data->start_class->invlist
+                                                = sv_2mortal(_new_invlist(0));
+                    }
+                    else {
+                        int complement = namedclass + ((invert) ? -1 : 1);
+
+                        assert(flags & SCF_DO_STCLASS_OR);
+
+                        /* If the complement of this class was already there,
+                         * the result is that they match all code points,
+                         * (\d + \D == everything).  Remove the classes from
+                         * future consideration.  Locale is not relevant in
+                         * this case */
+                        if (ANYOF_POSIXL_TEST(data->start_class, complement)) {
+                            ssc_match_all_cp(data->start_class);
+                            ANYOF_POSIXL_CLEAR(data->start_class, namedclass);
+                            ANYOF_POSIXL_CLEAR(data->start_class, complement);
+                        }
+                        else {  /* The usual case; just add this class to the
+                                   existing set */
+                            ANYOF_POSIXL_SET(data->start_class, namedclass);
+                        }
+                    }
+                    break;
+
+                case NPOSIXA:   /* For these, we always know the exact set of
+                                   what's matched */
+                    invert = 1;
+                    /* FALL THROUGH */
+               case POSIXA:
+                    if (FLAGS(scan) == _CC_ASCII) {
+                        my_invlist = invlist_clone(PL_XPosix_ptrs[_CC_ASCII]);
+                    }
+                    else {
+                        _invlist_intersection(PL_XPosix_ptrs[FLAGS(scan)],
+                                              PL_XPosix_ptrs[_CC_ASCII],
+                                              &my_invlist);
+                    }
+                    goto join_posix;
+
+               case NPOSIXD:
+               case NPOSIXU:
+                    invert = 1;
+                    /* FALL THROUGH */
+               case POSIXD:
+               case POSIXU:
+                    my_invlist = invlist_clone(PL_XPosix_ptrs[FLAGS(scan)]);
+
+                    /* NPOSIXD matches all upper Latin1 code points unless the
+                     * target string being matched is UTF-8, which is
+                     * unknowable until match time.  Since we are going to
+                     * invert, we want to get rid of all of them so that the
+                     * inversion will match all */
+                    if (OP(scan) == NPOSIXD) {
+                        _invlist_subtract(my_invlist, PL_UpperLatin1,
+                                          &my_invlist);
+                    }
+
+                  join_posix:
+
+                    if (flags & SCF_DO_STCLASS_AND) {
+                        ssc_intersection(data->start_class, my_invlist, invert);
+                        ssc_clear_locale(data->start_class);
+                    }
+                    else {
+                        assert(flags & SCF_DO_STCLASS_OR);
+                        ssc_union(data->start_class, my_invlist, invert);
+                    }
+                    SvREFCNT_dec(my_invlist);
+               }
+               if (flags & SCF_DO_STCLASS_OR)
+                   ssc_and(pRExC_state, data->start_class, (regnode_charclass *) and_withp);
+               flags &= ~SCF_DO_STCLASS;
+           }
+       }
+       else if (PL_regkind[OP(scan)] == EOL && flags & SCF_DO_SUBSTR) {
+           data->flags |= (OP(scan) == MEOL
+                           ? SF_BEFORE_MEOL
+                           : SF_BEFORE_SEOL);
+            scan_commit(pRExC_state, data, minlenp, is_inf);
+
+       }
+       else if (  PL_regkind[OP(scan)] == BRANCHJ
+                /* Lookbehind, or need to calculate parens/evals/stclass: */
+                  && (scan->flags || data || (flags & SCF_DO_STCLASS))
+                  && (OP(scan) == IFMATCH || OP(scan) == UNLESSM)) {
+            if ( OP(scan) == UNLESSM &&
+                 scan->flags == 0 &&
+                 OP(NEXTOPER(NEXTOPER(scan))) == NOTHING &&
+                 OP(regnext(NEXTOPER(NEXTOPER(scan)))) == SUCCEED
+            ) {
+                regnode *opt;
+                regnode *upto= regnext(scan);
+                DEBUG_PARSE_r({
+                    SV * const mysv_val=sv_newmortal();
+                    DEBUG_STUDYDATA("OPFAIL",data,depth);
+
+                    /*DEBUG_PARSE_MSG("opfail");*/
+                    regprop(RExC_rx, mysv_val, upto, NULL);
+                    PerlIO_printf(Perl_debug_log,
+                        "~ replace with OPFAIL pointed at %s (%"IVdf") offset %"IVdf"\n",
+                        SvPV_nolen_const(mysv_val),
+                        (IV)REG_NODE_NUM(upto),
+                        (IV)(upto - scan)
+                    );
+                });
+                OP(scan) = OPFAIL;
+                NEXT_OFF(scan) = upto - scan;
+                for (opt= scan + 1; opt < upto ; opt++)
+                    OP(opt) = OPTIMIZED;
+                scan= upto;
+                continue;
+            }
+            if ( !PERL_ENABLE_POSITIVE_ASSERTION_STUDY
+                || OP(scan) == UNLESSM )
+            {
+                /* Negative Lookahead/lookbehind
+                   In this case we can't do fixed string optimisation.
+                */
+
+                SSize_t deltanext, minnext, fake = 0;
+                regnode *nscan;
+                regnode_ssc intrnl;
+                int f = 0;
+
+                data_fake.flags = 0;
+                if (data) {
+                    data_fake.whilem_c = data->whilem_c;
+                    data_fake.last_closep = data->last_closep;
+               }
+                else
+                    data_fake.last_closep = &fake;
+               data_fake.pos_delta = delta;
+                if ( flags & SCF_DO_STCLASS && !scan->flags
+                     && OP(scan) == IFMATCH ) { /* Lookahead */
+                    ssc_init(pRExC_state, &intrnl);
+                    data_fake.start_class = &intrnl;
+                    f |= SCF_DO_STCLASS_AND;
+               }
+                if (flags & SCF_WHILEM_VISITED_POS)
+                    f |= SCF_WHILEM_VISITED_POS;
+                next = regnext(scan);
+                nscan = NEXTOPER(NEXTOPER(scan));
+                minnext = study_chunk(pRExC_state, &nscan, minlenp, &deltanext,
+                                      last, &data_fake, stopparen,
+                                      recursed_depth, NULL, f, depth+1);
+                if (scan->flags) {
+                    if (deltanext) {
+                       FAIL("Variable length lookbehind not implemented");
+                    }
+                    else if (minnext > (I32)U8_MAX) {
+                       FAIL2("Lookbehind longer than %"UVuf" not implemented",
+                              (UV)U8_MAX);
+                    }
+                    scan->flags = (U8)minnext;
+                }
+                if (data) {
+                    if (data_fake.flags & (SF_HAS_PAR|SF_IN_PAR))
+                        pars++;
+                    if (data_fake.flags & SF_HAS_EVAL)
+                        data->flags |= SF_HAS_EVAL;
+                    data->whilem_c = data_fake.whilem_c;
+                }
+                if (f & SCF_DO_STCLASS_AND) {
+                   if (flags & SCF_DO_STCLASS_OR) {
+                       /* OR before, AND after: ideally we would recurse with
+                        * data_fake to get the AND applied by study of the
+                        * remainder of the pattern, and then derecurse;
+                        * *** HACK *** for now just treat as "no information".
+                        * See [perl #56690].
+                        */
+                       ssc_init(pRExC_state, data->start_class);
+                   }  else {
+                        /* AND before and after: combine and continue.  These
+                         * assertions are zero-length, so can match an EMPTY
+                         * string */
+                       ssc_and(pRExC_state, data->start_class, (regnode_charclass *) &intrnl);
+                        ANYOF_FLAGS(data->start_class) |= ANYOF_EMPTY_STRING;
+                   }
+                }
+           }
+#if PERL_ENABLE_POSITIVE_ASSERTION_STUDY
+            else {
+                /* Positive Lookahead/lookbehind
+                   In this case we can do fixed string optimisation,
+                   but we must be careful about it. Note in the case of
+                   lookbehind the positions will be offset by the minimum
+                   length of the pattern, something we won't know about
+                   until after the recurse.
+                */
+                SSize_t deltanext, fake = 0;
+                regnode *nscan;
+                regnode_ssc intrnl;
+                int f = 0;
+                /* We use SAVEFREEPV so that when the full compile
+                    is finished perl will clean up the allocated
+                    minlens when it's all done. This way we don't
+                    have to worry about freeing them when we know
+                    they wont be used, which would be a pain.
+                 */
+                SSize_t *minnextp;
+                Newx( minnextp, 1, SSize_t );
+                SAVEFREEPV(minnextp);
+
+                if (data) {
+                    StructCopy(data, &data_fake, scan_data_t);
+                    if ((flags & SCF_DO_SUBSTR) && data->last_found) {
+                        f |= SCF_DO_SUBSTR;
+                        if (scan->flags)
+                            scan_commit(pRExC_state, &data_fake, minlenp, is_inf);
+                        data_fake.last_found=newSVsv(data->last_found);
+                    }
+                }
+                else
+                    data_fake.last_closep = &fake;
+                data_fake.flags = 0;
+               data_fake.pos_delta = delta;
+                if (is_inf)
+                   data_fake.flags |= SF_IS_INF;
+                if ( flags & SCF_DO_STCLASS && !scan->flags
+                     && OP(scan) == IFMATCH ) { /* Lookahead */
+                    ssc_init(pRExC_state, &intrnl);
+                    data_fake.start_class = &intrnl;
+                    f |= SCF_DO_STCLASS_AND;
+                }
+                if (flags & SCF_WHILEM_VISITED_POS)
+                    f |= SCF_WHILEM_VISITED_POS;
+                next = regnext(scan);
+                nscan = NEXTOPER(NEXTOPER(scan));
+
+                *minnextp = study_chunk(pRExC_state, &nscan, minnextp,
+                                        &deltanext, last, &data_fake,
+                                        stopparen, recursed_depth, NULL,
+                                        f,depth+1);
+                if (scan->flags) {
+                    if (deltanext) {
+                       FAIL("Variable length lookbehind not implemented");
+                    }
+                    else if (*minnextp > (I32)U8_MAX) {
+                       FAIL2("Lookbehind longer than %"UVuf" not implemented",
+                              (UV)U8_MAX);
+                    }
+                    scan->flags = (U8)*minnextp;
+                }
+
+                *minnextp += min;
+
+                if (f & SCF_DO_STCLASS_AND) {
+                    ssc_and(pRExC_state, data->start_class, (regnode_charclass *) &intrnl);
+                    ANYOF_FLAGS(data->start_class) |= ANYOF_EMPTY_STRING;
+                }
+                if (data) {
+                    if (data_fake.flags & (SF_HAS_PAR|SF_IN_PAR))
+                        pars++;
+                    if (data_fake.flags & SF_HAS_EVAL)
+                        data->flags |= SF_HAS_EVAL;
+                    data->whilem_c = data_fake.whilem_c;
+                    if ((flags & SCF_DO_SUBSTR) && data_fake.last_found) {
+                        if (RExC_rx->minlen<*minnextp)
+                            RExC_rx->minlen=*minnextp;
+                        scan_commit(pRExC_state, &data_fake, minnextp, is_inf);
+                        SvREFCNT_dec_NN(data_fake.last_found);
+
+                        if ( data_fake.minlen_fixed != minlenp )
+                        {
+                            data->offset_fixed= data_fake.offset_fixed;
+                            data->minlen_fixed= data_fake.minlen_fixed;
+                            data->lookbehind_fixed+= scan->flags;
+                        }
+                        if ( data_fake.minlen_float != minlenp )
+                        {
+                            data->minlen_float= data_fake.minlen_float;
+                            data->offset_float_min=data_fake.offset_float_min;
+                            data->offset_float_max=data_fake.offset_float_max;
+                            data->lookbehind_float+= scan->flags;
+                        }
+                    }
+                }
+           }
+#endif
+       }
+       else if (OP(scan) == OPEN) {
+           if (stopparen != (I32)ARG(scan))
+               pars++;
+       }
+       else if (OP(scan) == CLOSE) {
+           if (stopparen == (I32)ARG(scan)) {
+               break;
+           }
+           if ((I32)ARG(scan) == is_par) {
+               next = regnext(scan);
+
+               if ( next && (OP(next) != WHILEM) && next < last)
+                   is_par = 0;         /* Disable optimization */
+           }
+           if (data)
+               *(data->last_closep) = ARG(scan);
+       }
+       else if (OP(scan) == EVAL) {
+               if (data)
+                   data->flags |= SF_HAS_EVAL;
+       }
+       else if ( PL_regkind[OP(scan)] == ENDLIKE ) {
+           if (flags & SCF_DO_SUBSTR) {
+                scan_commit(pRExC_state, data, minlenp, is_inf);
+               flags &= ~SCF_DO_SUBSTR;
+           }
+           if (data && OP(scan)==ACCEPT) {
+               data->flags |= SCF_SEEN_ACCEPT;
+               if (stopmin > min)
+                   stopmin = min;
+           }
+       }
+       else if (OP(scan) == LOGICAL && scan->flags == 2) /* Embedded follows */
+       {
+               if (flags & SCF_DO_SUBSTR) {
+                    scan_commit(pRExC_state, data, minlenp, is_inf);
+                   data->longest = &(data->longest_float);
+               }
+               is_inf = is_inf_internal = 1;
+               if (flags & SCF_DO_STCLASS_OR) /* Allow everything */
+                   ssc_anything(data->start_class);
+               flags &= ~SCF_DO_STCLASS;
+       }
+       else if (OP(scan) == GPOS) {
+            if (!(RExC_rx->intflags & PREGf_GPOS_FLOAT) &&
+               !(delta || is_inf || (data && data->pos_delta)))
+           {
+                if (!(RExC_rx->intflags & PREGf_ANCH) && (flags & SCF_DO_SUBSTR))
+                    RExC_rx->intflags |= PREGf_ANCH_GPOS;
+               if (RExC_rx->gofs < (STRLEN)min)
+                   RExC_rx->gofs = min;
+            } else {
+                RExC_rx->intflags |= PREGf_GPOS_FLOAT;
+                RExC_rx->gofs = 0;
+            }
+       }
+#ifdef TRIE_STUDY_OPT
+#ifdef FULL_TRIE_STUDY
+        else if (PL_regkind[OP(scan)] == TRIE) {
+            /* NOTE - There is similar code to this block above for handling
+               BRANCH nodes on the initial study.  If you change stuff here
+               check there too. */
+            regnode *trie_node= scan;
+            regnode *tail= regnext(scan);
+            reg_trie_data *trie = (reg_trie_data*)RExC_rxi->data->data[ ARG(scan) ];
+            SSize_t max1 = 0, min1 = SSize_t_MAX;
+            regnode_ssc accum;
+
+            if (flags & SCF_DO_SUBSTR) { /* XXXX Add !SUSPEND? */
+                /* Cannot merge strings after this. */
+                scan_commit(pRExC_state, data, minlenp, is_inf);
+            }
+            if (flags & SCF_DO_STCLASS)
+                ssc_init_zero(pRExC_state, &accum);
+
+            if (!trie->jump) {
+                min1= trie->minlen;
+                max1= trie->maxlen;
+            } else {
+                const regnode *nextbranch= NULL;
+                U32 word;
+
+                for ( word=1 ; word <= trie->wordcount ; word++)
+                {
+                    SSize_t deltanext=0, minnext=0, f = 0, fake;
+                    regnode_ssc this_class;
+
+                    data_fake.flags = 0;
+                    if (data) {
+                        data_fake.whilem_c = data->whilem_c;
+                        data_fake.last_closep = data->last_closep;
+                    }
+                    else
+                        data_fake.last_closep = &fake;
+                   data_fake.pos_delta = delta;
+                    if (flags & SCF_DO_STCLASS) {
+                        ssc_init(pRExC_state, &this_class);
+                        data_fake.start_class = &this_class;
+                        f = SCF_DO_STCLASS_AND;
+                    }
+                    if (flags & SCF_WHILEM_VISITED_POS)
+                        f |= SCF_WHILEM_VISITED_POS;
+
+                    if (trie->jump[word]) {
+                        if (!nextbranch)
+                            nextbranch = trie_node + trie->jump[0];
+                        scan= trie_node + trie->jump[word];
+                        /* We go from the jump point to the branch that follows
+                           it. Note this means we need the vestigal unused
+                           branches even though they arent otherwise used. */
+                        minnext = study_chunk(pRExC_state, &scan, minlenp,
+                            &deltanext, (regnode *)nextbranch, &data_fake,
+                            stopparen, recursed_depth, NULL, f,depth+1);
+                    }
+                    if (nextbranch && PL_regkind[OP(nextbranch)]==BRANCH)
+                        nextbranch= regnext((regnode*)nextbranch);
+
+                    if (min1 > (SSize_t)(minnext + trie->minlen))
+                        min1 = minnext + trie->minlen;
+                    if (deltanext == SSize_t_MAX) {
+                        is_inf = is_inf_internal = 1;
+                        max1 = SSize_t_MAX;
+                    } else if (max1 < (SSize_t)(minnext + deltanext + trie->maxlen))
+                        max1 = minnext + deltanext + trie->maxlen;
+
+                    if (data_fake.flags & (SF_HAS_PAR|SF_IN_PAR))
+                        pars++;
+                    if (data_fake.flags & SCF_SEEN_ACCEPT) {
+                        if ( stopmin > min + min1)
+                           stopmin = min + min1;
+                       flags &= ~SCF_DO_SUBSTR;
+                       if (data)
+                           data->flags |= SCF_SEEN_ACCEPT;
+                   }
+                    if (data) {
+                        if (data_fake.flags & SF_HAS_EVAL)
+                            data->flags |= SF_HAS_EVAL;
+                        data->whilem_c = data_fake.whilem_c;
+                    }
+                    if (flags & SCF_DO_STCLASS)
+                        ssc_or(pRExC_state, &accum, (regnode_charclass *) &this_class);
+                }
+            }
+            if (flags & SCF_DO_SUBSTR) {
+                data->pos_min += min1;
+                data->pos_delta += max1 - min1;
+                if (max1 != min1 || is_inf)
+                    data->longest = &(data->longest_float);
+            }
+            min += min1;
+            delta += max1 - min1;
+            if (flags & SCF_DO_STCLASS_OR) {
+                ssc_or(pRExC_state, data->start_class, (regnode_charclass *) &accum);
+                if (min1) {
+                    ssc_and(pRExC_state, data->start_class, (regnode_charclass *) and_withp);
+                    flags &= ~SCF_DO_STCLASS;
+                }
+            }
+            else if (flags & SCF_DO_STCLASS_AND) {
+                if (min1) {
+                    ssc_and(pRExC_state, data->start_class, (regnode_charclass *) &accum);
+                    flags &= ~SCF_DO_STCLASS;
+                }
+                else {
+                    /* Switch to OR mode: cache the old value of
+                     * data->start_class */
+                   INIT_AND_WITHP;
+                    StructCopy(data->start_class, and_withp, regnode_ssc);
+                    flags &= ~SCF_DO_STCLASS_AND;
+                    StructCopy(&accum, data->start_class, regnode_ssc);
+                    flags |= SCF_DO_STCLASS_OR;
+                }
+            }
+            scan= tail;
+            continue;
+        }
+#else
+       else if (PL_regkind[OP(scan)] == TRIE) {
+           reg_trie_data *trie = (reg_trie_data*)RExC_rxi->data->data[ ARG(scan) ];
+           U8*bang=NULL;
+
+           min += trie->minlen;
+           delta += (trie->maxlen - trie->minlen);
+           flags &= ~SCF_DO_STCLASS; /* xxx */
+            if (flags & SCF_DO_SUBSTR) {
+                /* Cannot expect anything... */
+                scan_commit(pRExC_state, data, minlenp, is_inf);
+               data->pos_min += trie->minlen;
+               data->pos_delta += (trie->maxlen - trie->minlen);
+               if (trie->maxlen != trie->minlen)
+                   data->longest = &(data->longest_float);
+           }
+           if (trie->jump) /* no more substrings -- for now /grr*/
+               flags &= ~SCF_DO_SUBSTR;
+       }
+#endif /* old or new */
+#endif /* TRIE_STUDY_OPT */
+
+       /* Else: zero-length, ignore. */
+       scan = regnext(scan);
+    }
+    /* If we are exiting a recursion we can unset its recursed bit
+     * and allow ourselves to enter it again - no danger of an
+     * infinite loop there.
+    if (stopparen > -1 && recursed) {
+       DEBUG_STUDYDATA("unset:", data,depth);
+        PAREN_UNSET( recursed, stopparen);
+    }
+    */
+    if (frame) {
+        DEBUG_STUDYDATA("frame-end:",data,depth);
+        DEBUG_PEEP("fend", scan, depth);
+        /* restore previous context */
+        last = frame->last;
+        scan = frame->next;
+        stopparen = frame->stop;
+        recursed_depth = frame->prev_recursed_depth;
+        depth = depth - 1;
+
+        frame = frame->prev;
+        goto fake_study_recurse;
+    }
+
+  finish:
+    assert(!frame);
+    DEBUG_STUDYDATA("pre-fin:",data,depth);
+
+    *scanp = scan;
+    *deltap = is_inf_internal ? SSize_t_MAX : delta;
+
+    if (flags & SCF_DO_SUBSTR && is_inf)
+       data->pos_delta = SSize_t_MAX - data->pos_min;
+    if (is_par > (I32)U8_MAX)
+       is_par = 0;
+    if (is_par && pars==1 && data) {
+       data->flags |= SF_IN_PAR;
+       data->flags &= ~SF_HAS_PAR;
+    }
+    else if (pars && data) {
+       data->flags |= SF_HAS_PAR;
+       data->flags &= ~SF_IN_PAR;
+    }
+    if (flags & SCF_DO_STCLASS_OR)
+       ssc_and(pRExC_state, data->start_class, (regnode_charclass *) and_withp);
+    if (flags & SCF_TRIE_RESTUDY)
+        data->flags |=         SCF_TRIE_RESTUDY;
+
+    DEBUG_STUDYDATA("post-fin:",data,depth);
+
+    {
+        SSize_t final_minlen= min < stopmin ? min : stopmin;
+
+        if (!(RExC_seen & REG_UNBOUNDED_QUANTIFIER_SEEN) && (RExC_maxlen < final_minlen + delta)) {
+            RExC_maxlen = final_minlen + delta;
+        }
+        return final_minlen;
+    }
+    /* not-reached */
+}
+
+STATIC U32
+S_add_data(RExC_state_t* const pRExC_state, const char* const s, const U32 n)
+{
+    U32 count = RExC_rxi->data ? RExC_rxi->data->count : 0;
+
+    PERL_ARGS_ASSERT_ADD_DATA;
+
+    Renewc(RExC_rxi->data,
+          sizeof(*RExC_rxi->data) + sizeof(void*) * (count + n - 1),
+          char, struct reg_data);
+    if(count)
+       Renew(RExC_rxi->data->what, count + n, U8);
+    else
+       Newx(RExC_rxi->data->what, n, U8);
+    RExC_rxi->data->count = count + n;
+    Copy(s, RExC_rxi->data->what + count, n, U8);
+    return count;
+}
+
+/*XXX: todo make this not included in a non debugging perl */
+#ifndef PERL_IN_XSUB_RE
+void
+Perl_reginitcolors(pTHX)
+{
+    dVAR;
+    const char * const s = PerlEnv_getenv("PERL_RE_COLORS");
+    if (s) {
+       char *t = savepv(s);
+       int i = 0;
+       PL_colors[0] = t;
+       while (++i < 6) {
+           t = strchr(t, '\t');
+           if (t) {
+               *t = '\0';
+               PL_colors[i] = ++t;
+           }
+           else
+               PL_colors[i] = t = (char *)"";
+       }
+    } else {
+       int i = 0;
+       while (i < 6)
+           PL_colors[i++] = (char *)"";
+    }
+    PL_colorset = 1;
+}
+#endif
+
+
+#ifdef TRIE_STUDY_OPT
+#define CHECK_RESTUDY_GOTO_butfirst(dOsomething)            \
+    STMT_START {                                            \
+        if (                                                \
+              (data.flags & SCF_TRIE_RESTUDY)               \
+              && ! restudied++                              \
+        ) {                                                 \
+            dOsomething;                                    \
+            goto reStudy;                                   \
+        }                                                   \
+    } STMT_END
+#else
+#define CHECK_RESTUDY_GOTO_butfirst
+#endif
+
+/*
+ * pregcomp - compile a regular expression into internal code
+ *
+ * Decides which engine's compiler to call based on the hint currently in
+ * scope
+ */
+
+#ifndef PERL_IN_XSUB_RE
+
+/* return the currently in-scope regex engine (or the default if none)  */
+
+regexp_engine const *
+Perl_current_re_engine(pTHX)
+{
+    dVAR;
+
+    if (IN_PERL_COMPILETIME) {
+       HV * const table = GvHV(PL_hintgv);
+       SV **ptr;
+
+       if (!table || !(PL_hints & HINT_LOCALIZE_HH))
+           return &PL_core_reg_engine;
+       ptr = hv_fetchs(table, "regcomp", FALSE);
+       if ( !(ptr && SvIOK(*ptr) && SvIV(*ptr)))
+           return &PL_core_reg_engine;
+       return INT2PTR(regexp_engine*,SvIV(*ptr));
+    }
+    else {
+       SV *ptr;
+       if (!PL_curcop->cop_hints_hash)
+           return &PL_core_reg_engine;
+       ptr = cop_hints_fetch_pvs(PL_curcop, "regcomp", 0);
+       if ( !(ptr && SvIOK(ptr) && SvIV(ptr)))
+           return &PL_core_reg_engine;
+       return INT2PTR(regexp_engine*,SvIV(ptr));
+    }
+}
+
+
+REGEXP *
+Perl_pregcomp(pTHX_ SV * const pattern, const U32 flags)
+{
+    dVAR;
+    regexp_engine const *eng = current_re_engine();
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_PREGCOMP;
+
+    /* Dispatch a request to compile a regexp to correct regexp engine. */
+    DEBUG_COMPILE_r({
+       PerlIO_printf(Perl_debug_log, "Using engine %"UVxf"\n",
+                       PTR2UV(eng));
+    });
+    return CALLREGCOMP_ENG(eng, pattern, flags);
+}
+#endif
+
+/* public(ish) entry point for the perl core's own regex compiling code.
+ * It's actually a wrapper for Perl_re_op_compile that only takes an SV
+ * pattern rather than a list of OPs, and uses the internal engine rather
+ * than the current one */
+
+REGEXP *
+Perl_re_compile(pTHX_ SV * const pattern, U32 rx_flags)
+{
+    SV *pat = pattern; /* defeat constness! */
+    PERL_ARGS_ASSERT_RE_COMPILE;
+    return Perl_re_op_compile(aTHX_ &pat, 1, NULL,
+#ifdef PERL_IN_XSUB_RE
+                                &my_reg_engine,
+#else
+                                &PL_core_reg_engine,
+#endif
+                                NULL, NULL, rx_flags, 0);
+}
+
+
+/* upgrade pattern pat_p of length plen_p to UTF8, and if there are code
+ * blocks, recalculate the indices. Update pat_p and plen_p in-place to
+ * point to the realloced string and length.
+ *
+ * This is essentially a copy of Perl_bytes_to_utf8() with the code index
+ * stuff added */
+
+static void
+S_pat_upgrade_to_utf8(pTHX_ RExC_state_t * const pRExC_state,
+                   char **pat_p, STRLEN *plen_p, int num_code_blocks)
+{
+    U8 *const src = (U8*)*pat_p;
+    U8 *dst;
+    int n=0;
+    STRLEN s = 0, d = 0;
+    bool do_end = 0;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    DEBUG_PARSE_r(PerlIO_printf(Perl_debug_log,
+        "UTF8 mismatch! Converting to utf8 for resizing and compile\n"));
+
+    Newx(dst, *plen_p * 2 + 1, U8);
+
+    while (s < *plen_p) {
+        if (NATIVE_BYTE_IS_INVARIANT(src[s]))
+            dst[d]   = src[s];
+        else {
+            dst[d++] = UTF8_EIGHT_BIT_HI(src[s]);
+            dst[d]   = UTF8_EIGHT_BIT_LO(src[s]);
+        }
+        if (n < num_code_blocks) {
+            if (!do_end && pRExC_state->code_blocks[n].start == s) {
+                pRExC_state->code_blocks[n].start = d;
+                assert(dst[d] == '(');
+                do_end = 1;
+            }
+            else if (do_end && pRExC_state->code_blocks[n].end == s) {
+                pRExC_state->code_blocks[n].end = d;
+                assert(dst[d] == ')');
+                do_end = 0;
+                n++;
+            }
+        }
+        s++;
+        d++;
+    }
+    dst[d] = '\0';
+    *plen_p = d;
+    *pat_p = (char*) dst;
+    SAVEFREEPV(*pat_p);
+    RExC_orig_utf8 = RExC_utf8 = 1;
+}
+
+
+
+/* S_concat_pat(): concatenate a list of args to the pattern string pat,
+ * while recording any code block indices, and handling overloading,
+ * nested qr// objects etc.  If pat is null, it will allocate a new
+ * string, or just return the first arg, if there's only one.
+ *
+ * Returns the malloced/updated pat.
+ * patternp and pat_count is the array of SVs to be concatted;
+ * oplist is the optional list of ops that generated the SVs;
+ * recompile_p is a pointer to a boolean that will be set if
+ *   the regex will need to be recompiled.
+ * delim, if non-null is an SV that will be inserted between each element
+ */
+
+static SV*
+S_concat_pat(pTHX_ RExC_state_t * const pRExC_state,
+                SV *pat, SV ** const patternp, int pat_count,
+                OP *oplist, bool *recompile_p, SV *delim)
+{
+    SV **svp;
+    int n = 0;
+    bool use_delim = FALSE;
+    bool alloced = FALSE;
+
+    /* if we know we have at least two args, create an empty string,
+     * then concatenate args to that. For no args, return an empty string */
+    if (!pat && pat_count != 1) {
+        pat = newSVpvn("", 0);
+        SAVEFREESV(pat);
+        alloced = TRUE;
+    }
+
+    for (svp = patternp; svp < patternp + pat_count; svp++) {
+        SV *sv;
+        SV *rx  = NULL;
+        STRLEN orig_patlen = 0;
+        bool code = 0;
+        SV *msv = use_delim ? delim : *svp;
+        if (!msv) msv = &PL_sv_undef;
+
+        /* if we've got a delimiter, we go round the loop twice for each
+         * svp slot (except the last), using the delimiter the second
+         * time round */
+        if (use_delim) {
+            svp--;
+            use_delim = FALSE;
+        }
+        else if (delim)
+            use_delim = TRUE;
+
+        if (SvTYPE(msv) == SVt_PVAV) {
+            /* we've encountered an interpolated array within
+             * the pattern, e.g. /...@a..../. Expand the list of elements,
+             * then recursively append elements.
+             * The code in this block is based on S_pushav() */
+
+            AV *const av = (AV*)msv;
+            const SSize_t maxarg = AvFILL(av) + 1;
+            SV **array;
+
+            if (oplist) {
+                assert(oplist->op_type == OP_PADAV
+                    || oplist->op_type == OP_RV2AV);
+                oplist = oplist->op_sibling;;
+            }
+
+            if (SvRMAGICAL(av)) {
+                SSize_t i;
+
+                Newx(array, maxarg, SV*);
+                SAVEFREEPV(array);
+                for (i=0; i < maxarg; i++) {
+                    SV ** const svp = av_fetch(av, i, FALSE);
+                    array[i] = svp ? *svp : &PL_sv_undef;
+                }
+            }
+            else
+                array = AvARRAY(av);
+
+            pat = S_concat_pat(aTHX_ pRExC_state, pat,
+                                array, maxarg, NULL, recompile_p,
+                                /* $" */
+                                GvSV((gv_fetchpvs("\"", GV_ADDMULTI, SVt_PV))));
+
+            continue;
+        }
+
+
+        /* we make the assumption here that each op in the list of
+         * op_siblings maps to one SV pushed onto the stack,
+         * except for code blocks, with have both an OP_NULL and
+         * and OP_CONST.
+         * This allows us to match up the list of SVs against the
+         * list of OPs to find the next code block.
+         *
+         * Note that       PUSHMARK PADSV PADSV ..
+         * is optimised to
+         *                 PADRANGE PADSV  PADSV  ..
+         * so the alignment still works. */
+
+        if (oplist) {
+            if (oplist->op_type == OP_NULL
+                && (oplist->op_flags & OPf_SPECIAL))
+            {
+                assert(n < pRExC_state->num_code_blocks);
+                pRExC_state->code_blocks[n].start = pat ? SvCUR(pat) : 0;
+                pRExC_state->code_blocks[n].block = oplist;
+                pRExC_state->code_blocks[n].src_regex = NULL;
+                n++;
+                code = 1;
+                oplist = oplist->op_sibling; /* skip CONST */
+                assert(oplist);
+            }
+            oplist = oplist->op_sibling;;
+        }
+
+       /* apply magic and QR overloading to arg */
+
+        SvGETMAGIC(msv);
+        if (SvROK(msv) && SvAMAGIC(msv)) {
+            SV *sv = AMG_CALLunary(msv, regexp_amg);
+            if (sv) {
+                if (SvROK(sv))
+                    sv = SvRV(sv);
+                if (SvTYPE(sv) != SVt_REGEXP)
+                    Perl_croak(aTHX_ "Overloaded qr did not return a REGEXP");
+                msv = sv;
+            }
+        }
+
+        /* try concatenation overload ... */
+        if (pat && (SvAMAGIC(pat) || SvAMAGIC(msv)) &&
+                (sv = amagic_call(pat, msv, concat_amg, AMGf_assign)))
+        {
+            sv_setsv(pat, sv);
+            /* overloading involved: all bets are off over literal
+             * code. Pretend we haven't seen it */
+            pRExC_state->num_code_blocks -= n;
+            n = 0;
+        }
+        else  {
+            /* ... or failing that, try "" overload */
+            while (SvAMAGIC(msv)
+                    && (sv = AMG_CALLunary(msv, string_amg))
+                    && sv != msv
+                    &&  !(   SvROK(msv)
+                          && SvROK(sv)
+                          && SvRV(msv) == SvRV(sv))
+            ) {
+                msv = sv;
+                SvGETMAGIC(msv);
+            }
+            if (SvROK(msv) && SvTYPE(SvRV(msv)) == SVt_REGEXP)
+                msv = SvRV(msv);
+
+            if (pat) {
+                /* this is a partially unrolled
+                 *     sv_catsv_nomg(pat, msv);
+                 * that allows us to adjust code block indices if
+                 * needed */
+                STRLEN dlen;
+                char *dst = SvPV_force_nomg(pat, dlen);
+                orig_patlen = dlen;
+                if (SvUTF8(msv) && !SvUTF8(pat)) {
+                    S_pat_upgrade_to_utf8(aTHX_ pRExC_state, &dst, &dlen, n);
+                    sv_setpvn(pat, dst, dlen);
+                    SvUTF8_on(pat);
+                }
+                sv_catsv_nomg(pat, msv);
+                rx = msv;
+            }
+            else
+                pat = msv;
+
+            if (code)
+                pRExC_state->code_blocks[n-1].end = SvCUR(pat)-1;
+        }
+
+        /* extract any code blocks within any embedded qr//'s */
+        if (rx && SvTYPE(rx) == SVt_REGEXP
+            && RX_ENGINE((REGEXP*)rx)->op_comp)
+        {
+
+            RXi_GET_DECL(ReANY((REGEXP *)rx), ri);
+            if (ri->num_code_blocks) {
+                int i;
+                /* the presence of an embedded qr// with code means
+                 * we should always recompile: the text of the
+                 * qr// may not have changed, but it may be a
+                 * different closure than last time */
+                *recompile_p = 1;
+                Renew(pRExC_state->code_blocks,
+                    pRExC_state->num_code_blocks + ri->num_code_blocks,
+                    struct reg_code_block);
+                pRExC_state->num_code_blocks += ri->num_code_blocks;
+
+                for (i=0; i < ri->num_code_blocks; i++) {
+                    struct reg_code_block *src, *dst;
+                    STRLEN offset =  orig_patlen
+                        + ReANY((REGEXP *)rx)->pre_prefix;
+                    assert(n < pRExC_state->num_code_blocks);
+                    src = &ri->code_blocks[i];
+                    dst = &pRExC_state->code_blocks[n];
+                    dst->start     = src->start + offset;
+                    dst->end       = src->end   + offset;
+                    dst->block     = src->block;
+                    dst->src_regex  = (REGEXP*) SvREFCNT_inc( (SV*)
+                                            src->src_regex
+                                                ? src->src_regex
+                                                : (REGEXP*)rx);
+                    n++;
+                }
+            }
+        }
+    }
+    /* avoid calling magic multiple times on a single element e.g. =~ $qr */
+    if (alloced)
+        SvSETMAGIC(pat);
+
+    return pat;
+}
+
+
+
+/* see if there are any run-time code blocks in the pattern.
+ * False positives are allowed */
+
+static bool
+S_has_runtime_code(pTHX_ RExC_state_t * const pRExC_state,
+                   char *pat, STRLEN plen)
+{
+    int n = 0;
+    STRLEN s;
+
+    for (s = 0; s < plen; s++) {
+       if (n < pRExC_state->num_code_blocks
+           && s == pRExC_state->code_blocks[n].start)
+       {
+           s = pRExC_state->code_blocks[n].end;
+           n++;
+           continue;
+       }
+       /* TODO ideally should handle [..], (#..), /#.../x to reduce false
+        * positives here */
+       if (pat[s] == '(' && s+2 <= plen && pat[s+1] == '?' &&
+           (pat[s+2] == '{'
+                || (s + 2 <= plen && pat[s+2] == '?' && pat[s+3] == '{'))
+       )
+           return 1;
+    }
+    return 0;
+}
+
+/* Handle run-time code blocks. We will already have compiled any direct
+ * or indirect literal code blocks. Now, take the pattern 'pat' and make a
+ * copy of it, but with any literal code blocks blanked out and
+ * appropriate chars escaped; then feed it into
+ *
+ *    eval "qr'modified_pattern'"
+ *
+ * For example,
+ *
+ *       a\bc(?{"this was literal"})def'ghi\\jkl(?{"this is runtime"})mno
+ *
+ * becomes
+ *
+ *    qr'a\\bc_______________________def\'ghi\\\\jkl(?{"this is runtime"})mno'
+ *
+ * After eval_sv()-ing that, grab any new code blocks from the returned qr
+ * and merge them with any code blocks of the original regexp.
+ *
+ * If the pat is non-UTF8, while the evalled qr is UTF8, don't merge;
+ * instead, just save the qr and return FALSE; this tells our caller that
+ * the original pattern needs upgrading to utf8.
+ */
+
+static bool
+S_compile_runtime_code(pTHX_ RExC_state_t * const pRExC_state,
+    char *pat, STRLEN plen)
+{
+    SV *qr;
+
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    if (pRExC_state->runtime_code_qr) {
+       /* this is the second time we've been called; this should
+        * only happen if the main pattern got upgraded to utf8
+        * during compilation; re-use the qr we compiled first time
+        * round (which should be utf8 too)
+        */
+       qr = pRExC_state->runtime_code_qr;
+       pRExC_state->runtime_code_qr = NULL;
+       assert(RExC_utf8 && SvUTF8(qr));
+    }
+    else {
+       int n = 0;
+       STRLEN s;
+       char *p, *newpat;
+       int newlen = plen + 6; /* allow for "qr''x\0" extra chars */
+       SV *sv, *qr_ref;
+       dSP;
+
+       /* determine how many extra chars we need for ' and \ escaping */
+       for (s = 0; s < plen; s++) {
+           if (pat[s] == '\'' || pat[s] == '\\')
+               newlen++;
+       }
+
+       Newx(newpat, newlen, char);
+       p = newpat;
+       *p++ = 'q'; *p++ = 'r'; *p++ = '\'';
+
+       for (s = 0; s < plen; s++) {
+           if (n < pRExC_state->num_code_blocks
+               && s == pRExC_state->code_blocks[n].start)
+           {
+               /* blank out literal code block */
+               assert(pat[s] == '(');
+               while (s <= pRExC_state->code_blocks[n].end) {
+                   *p++ = '_';
+                   s++;
+               }
+               s--;
+               n++;
+               continue;
+           }
+           if (pat[s] == '\'' || pat[s] == '\\')
+               *p++ = '\\';
+           *p++ = pat[s];
+       }
+       *p++ = '\'';
+       if (pRExC_state->pm_flags & RXf_PMf_EXTENDED)
+           *p++ = 'x';
+       *p++ = '\0';
+       DEBUG_COMPILE_r({
+           PerlIO_printf(Perl_debug_log,
+               "%sre-parsing pattern for runtime code:%s %s\n",
+               PL_colors[4],PL_colors[5],newpat);
+       });
+
+       sv = newSVpvn_flags(newpat, p-newpat-1, RExC_utf8 ? SVf_UTF8 : 0);
+       Safefree(newpat);
+
+       ENTER;
+       SAVETMPS;
+       save_re_context();
+       PUSHSTACKi(PERLSI_REQUIRE);
+        /* G_RE_REPARSING causes the toker to collapse \\ into \ when
+         * parsing qr''; normally only q'' does this. It also alters
+         * hints handling */
+       eval_sv(sv, G_SCALAR|G_RE_REPARSING);
+       SvREFCNT_dec_NN(sv);
+       SPAGAIN;
+       qr_ref = POPs;
+       PUTBACK;
+       {
+           SV * const errsv = ERRSV;
+           if (SvTRUE_NN(errsv))
+           {
+               Safefree(pRExC_state->code_blocks);
+                /* use croak_sv ? */
+               Perl_croak_nocontext("%"SVf, SVfARG(errsv));
+           }
+       }
+       assert(SvROK(qr_ref));
+       qr = SvRV(qr_ref);
+       assert(SvTYPE(qr) == SVt_REGEXP && RX_ENGINE((REGEXP*)qr)->op_comp);
+       /* the leaving below frees the tmp qr_ref.
+        * Give qr a life of its own */
+       SvREFCNT_inc(qr);
+       POPSTACK;
+       FREETMPS;
+       LEAVE;
+
+    }
+
+    if (!RExC_utf8 && SvUTF8(qr)) {
+       /* first time through; the pattern got upgraded; save the
+        * qr for the next time through */
+       assert(!pRExC_state->runtime_code_qr);
+       pRExC_state->runtime_code_qr = qr;
+       return 0;
+    }
+
+
+    /* extract any code blocks within the returned qr//  */
+
+
+    /* merge the main (r1) and run-time (r2) code blocks into one */
+    {
+       RXi_GET_DECL(ReANY((REGEXP *)qr), r2);
+       struct reg_code_block *new_block, *dst;
+       RExC_state_t * const r1 = pRExC_state; /* convenient alias */
+       int i1 = 0, i2 = 0;
+
+       if (!r2->num_code_blocks) /* we guessed wrong */
+       {
+           SvREFCNT_dec_NN(qr);
+           return 1;
+       }
+
+       Newx(new_block,
+           r1->num_code_blocks + r2->num_code_blocks,
+           struct reg_code_block);
+       dst = new_block;
+
+       while (    i1 < r1->num_code_blocks
+               || i2 < r2->num_code_blocks)
+       {
+           struct reg_code_block *src;
+           bool is_qr = 0;
+
+           if (i1 == r1->num_code_blocks) {
+               src = &r2->code_blocks[i2++];
+               is_qr = 1;
+           }
+           else if (i2 == r2->num_code_blocks)
+               src = &r1->code_blocks[i1++];
+           else if (  r1->code_blocks[i1].start
+                    < r2->code_blocks[i2].start)
+           {
+               src = &r1->code_blocks[i1++];
+               assert(src->end < r2->code_blocks[i2].start);
+           }
+           else {
+               assert(  r1->code_blocks[i1].start
+                      > r2->code_blocks[i2].start);
+               src = &r2->code_blocks[i2++];
+               is_qr = 1;
+               assert(src->end < r1->code_blocks[i1].start);
+           }
+
+           assert(pat[src->start] == '(');
+           assert(pat[src->end]   == ')');
+           dst->start      = src->start;
+           dst->end        = src->end;
+           dst->block      = src->block;
+           dst->src_regex  = is_qr ? (REGEXP*) SvREFCNT_inc( (SV*) qr)
+                                   : src->src_regex;
+           dst++;
+       }
+       r1->num_code_blocks += r2->num_code_blocks;
+       Safefree(r1->code_blocks);
+       r1->code_blocks = new_block;
+    }
+
+    SvREFCNT_dec_NN(qr);
+    return 1;
+}
+
+
+STATIC bool
+S_setup_longest(pTHX_ RExC_state_t *pRExC_state, SV* sv_longest,
+                      SV** rx_utf8, SV** rx_substr, SSize_t* rx_end_shift,
+                     SSize_t lookbehind, SSize_t offset, SSize_t *minlen,
+                      STRLEN longest_length, bool eol, bool meol)
+{
+    /* This is the common code for setting up the floating and fixed length
+     * string data extracted from Perl_re_op_compile() below.  Returns a boolean
+     * as to whether succeeded or not */
+
+    I32 t;
+    SSize_t ml;
+
+    if (! (longest_length
+           || (eol /* Can't have SEOL and MULTI */
+               && (! meol || (RExC_flags & RXf_PMf_MULTILINE)))
+          )
+            /* See comments for join_exact for why REG_UNFOLDED_MULTI_SEEN */
+        || (RExC_seen & REG_UNFOLDED_MULTI_SEEN))
+    {
+        return FALSE;
+    }
+
+    /* copy the information about the longest from the reg_scan_data
+        over to the program. */
+    if (SvUTF8(sv_longest)) {
+        *rx_utf8 = sv_longest;
+        *rx_substr = NULL;
+    } else {
+        *rx_substr = sv_longest;
+        *rx_utf8 = NULL;
+    }
+    /* end_shift is how many chars that must be matched that
+        follow this item. We calculate it ahead of time as once the
+        lookbehind offset is added in we lose the ability to correctly
+        calculate it.*/
+    ml = minlen ? *(minlen) : (SSize_t)longest_length;
+    *rx_end_shift = ml - offset
+        - longest_length + (SvTAIL(sv_longest) != 0)
+        + lookbehind;
+
+    t = (eol/* Can't have SEOL and MULTI */
+         && (! meol || (RExC_flags & RXf_PMf_MULTILINE)));
+    fbm_compile(sv_longest, t ? FBMcf_TAIL : 0);
+
+    return TRUE;
+}
+
+/*
+ * Perl_re_op_compile - the perl internal RE engine's function to compile a
+ * regular expression into internal code.
+ * The pattern may be passed either as:
+ *    a list of SVs (patternp plus pat_count)
+ *    a list of OPs (expr)
+ * If both are passed, the SV list is used, but the OP list indicates
+ * which SVs are actually pre-compiled code blocks
+ *
+ * The SVs in the list have magic and qr overloading applied to them (and
+ * the list may be modified in-place with replacement SVs in the latter
+ * case).
+ *
+ * If the pattern hasn't changed from old_re, then old_re will be
+ * returned.
+ *
+ * eng is the current engine. If that engine has an op_comp method, then
+ * handle directly (i.e. we assume that op_comp was us); otherwise, just
+ * do the initial concatenation of arguments and pass on to the external
+ * engine.
+ *
+ * If is_bare_re is not null, set it to a boolean indicating whether the
+ * arg list reduced (after overloading) to a single bare regex which has
+ * been returned (i.e. /$qr/).
+ *
+ * orig_rx_flags contains RXf_* flags. See perlreapi.pod for more details.
+ *
+ * pm_flags contains the PMf_* flags, typically based on those from the
+ * pm_flags field of the related PMOP. Currently we're only interested in
+ * PMf_HAS_CV, PMf_IS_QR, PMf_USE_RE_EVAL.
+ *
+ * We can't allocate space until we know how big the compiled form will be,
+ * but we can't compile it (and thus know how big it is) until we've got a
+ * place to put the code.  So we cheat:  we compile it twice, once with code
+ * generation turned off and size counting turned on, and once "for real".
+ * This also means that we don't allocate space until we are sure that the
+ * thing really will compile successfully, and we never have to move the
+ * code and thus invalidate pointers into it.  (Note that it has to be in
+ * one piece because free() must be able to free it all.) [NB: not true in perl]
+ *
+ * Beware that the optimization-preparation code in here knows about some
+ * of the structure of the compiled regexp.  [I'll say.]
+ */
+
+REGEXP *
+Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
+                   OP *expr, const regexp_engine* eng, REGEXP *old_re,
+                    bool *is_bare_re, U32 orig_rx_flags, U32 pm_flags)
+{
+    dVAR;
+    REGEXP *rx;
+    struct regexp *r;
+    regexp_internal *ri;
+    STRLEN plen;
+    char *exp;
+    regnode *scan;
+    I32 flags;
+    SSize_t minlen = 0;
+    U32 rx_flags;
+    SV *pat;
+    SV *code_blocksv = NULL;
+    SV** new_patternp = patternp;
+
+    /* these are all flags - maybe they should be turned
+     * into a single int with different bit masks */
+    I32 sawlookahead = 0;
+    I32 sawplus = 0;
+    I32 sawopen = 0;
+    I32 sawminmod = 0;
+
+    regex_charset initial_charset = get_regex_charset(orig_rx_flags);
+    bool recompile = 0;
+    bool runtime_code = 0;
+    scan_data_t data;
+    RExC_state_t RExC_state;
+    RExC_state_t * const pRExC_state = &RExC_state;
+#ifdef TRIE_STUDY_OPT
+    int restudied = 0;
+    RExC_state_t copyRExC_state;
+#endif
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_RE_OP_COMPILE;
+
+    DEBUG_r(if (!PL_colorset) reginitcolors());
+
+#ifndef PERL_IN_XSUB_RE
+    /* Initialize these here instead of as-needed, as is quick and avoids
+     * having to test them each time otherwise */
+    if (! PL_AboveLatin1) {
+       PL_AboveLatin1 = _new_invlist_C_array(AboveLatin1_invlist);
+       PL_Latin1 = _new_invlist_C_array(Latin1_invlist);
+       PL_UpperLatin1 = _new_invlist_C_array(UpperLatin1_invlist);
+        PL_utf8_foldable = _new_invlist_C_array(_Perl_Any_Folds_invlist);
+        PL_HasMultiCharFold =
+                       _new_invlist_C_array(_Perl_Folds_To_Multi_Char_invlist);
+    }
+#endif
+
+    pRExC_state->code_blocks = NULL;
+    pRExC_state->num_code_blocks = 0;
+
+    if (is_bare_re)
+       *is_bare_re = FALSE;
+
+    if (expr && (expr->op_type == OP_LIST ||
+               (expr->op_type == OP_NULL && expr->op_targ == OP_LIST))) {
+       /* allocate code_blocks if needed */
+       OP *o;
+       int ncode = 0;
+
+       for (o = cLISTOPx(expr)->op_first; o; o = o->op_sibling)
+           if (o->op_type == OP_NULL && (o->op_flags & OPf_SPECIAL))
+               ncode++; /* count of DO blocks */
+       if (ncode) {
+           pRExC_state->num_code_blocks = ncode;
+           Newx(pRExC_state->code_blocks, ncode, struct reg_code_block);
+       }
+    }
+
+    if (!pat_count) {
+        /* compile-time pattern with just OP_CONSTs and DO blocks */
+
+        int n;
+        OP *o;
+
+        /* find how many CONSTs there are */
+        assert(expr);
+        n = 0;
+        if (expr->op_type == OP_CONST)
+            n = 1;
+        else
+            for (o = cLISTOPx(expr)->op_first; o; o = o->op_sibling) {
+                if (o->op_type == OP_CONST)
+                    n++;
+            }
+
+        /* fake up an SV array */
+
+        assert(!new_patternp);
+        Newx(new_patternp, n, SV*);
+        SAVEFREEPV(new_patternp);
+        pat_count = n;
+
+        n = 0;
+        if (expr->op_type == OP_CONST)
+            new_patternp[n] = cSVOPx_sv(expr);
+        else
+            for (o = cLISTOPx(expr)->op_first; o; o = o->op_sibling) {
+                if (o->op_type == OP_CONST)
+                    new_patternp[n++] = cSVOPo_sv;
+            }
+
+    }
+
+    DEBUG_PARSE_r(PerlIO_printf(Perl_debug_log,
+        "Assembling pattern from %d elements%s\n", pat_count,
+            orig_rx_flags & RXf_SPLIT ? " for split" : ""));
+
+    /* set expr to the first arg op */
+
+    if (pRExC_state->num_code_blocks
+         && expr->op_type != OP_CONST)
+    {
+            expr = cLISTOPx(expr)->op_first;
+            assert(   expr->op_type == OP_PUSHMARK
+                   || (expr->op_type == OP_NULL && expr->op_targ == OP_PUSHMARK)
+                   || expr->op_type == OP_PADRANGE);
+            expr = expr->op_sibling;
+    }
+
+    pat = S_concat_pat(aTHX_ pRExC_state, NULL, new_patternp, pat_count,
+                        expr, &recompile, NULL);
+
+    /* handle bare (possibly after overloading) regex: foo =~ $re */
+    {
+        SV *re = pat;
+        if (SvROK(re))
+            re = SvRV(re);
+        if (SvTYPE(re) == SVt_REGEXP) {
+            if (is_bare_re)
+                *is_bare_re = TRUE;
+            SvREFCNT_inc(re);
+            Safefree(pRExC_state->code_blocks);
+            DEBUG_PARSE_r(PerlIO_printf(Perl_debug_log,
+                "Precompiled pattern%s\n",
+                    orig_rx_flags & RXf_SPLIT ? " for split" : ""));
+
+            return (REGEXP*)re;
+        }
+    }
+
+    exp = SvPV_nomg(pat, plen);
+
+    if (!eng->op_comp) {
+       if ((SvUTF8(pat) && IN_BYTES)
+               || SvGMAGICAL(pat) || SvAMAGIC(pat))
+       {
+           /* make a temporary copy; either to convert to bytes,
+            * or to avoid repeating get-magic / overloaded stringify */
+           pat = newSVpvn_flags(exp, plen, SVs_TEMP |
+                                       (IN_BYTES ? 0 : SvUTF8(pat)));
+       }
+       Safefree(pRExC_state->code_blocks);
+       return CALLREGCOMP_ENG(eng, pat, orig_rx_flags);
+    }
+
+    /* ignore the utf8ness if the pattern is 0 length */
+    RExC_utf8 = RExC_orig_utf8 = (plen == 0 || IN_BYTES) ? 0 : SvUTF8(pat);
+    RExC_uni_semantics = 0;
+    RExC_contains_locale = 0;
+    RExC_contains_i = 0;
+    pRExC_state->runtime_code_qr = NULL;
+
+    DEBUG_COMPILE_r({
+            SV *dsv= sv_newmortal();
+            RE_PV_QUOTED_DECL(s, RExC_utf8, dsv, exp, plen, 60);
+            PerlIO_printf(Perl_debug_log, "%sCompiling REx%s %s\n",
+                          PL_colors[4],PL_colors[5],s);
+        });
+
+  redo_first_pass:
+    /* we jump here if we upgrade the pattern to utf8 and have to
+     * recompile */
+
+    if ((pm_flags & PMf_USE_RE_EVAL)
+               /* this second condition covers the non-regex literal case,
+                * i.e.  $foo =~ '(?{})'. */
+               || (IN_PERL_COMPILETIME && (PL_hints & HINT_RE_EVAL))
+    )
+       runtime_code = S_has_runtime_code(aTHX_ pRExC_state, exp, plen);
+
+    /* return old regex if pattern hasn't changed */
+    /* XXX: note in the below we have to check the flags as well as the
+     * pattern.
+     *
+     * Things get a touch tricky as we have to compare the utf8 flag
+     * independently from the compile flags.  */
+
+    if (   old_re
+        && !recompile
+        && !!RX_UTF8(old_re) == !!RExC_utf8
+        && ( RX_COMPFLAGS(old_re) == ( orig_rx_flags & RXf_PMf_FLAGCOPYMASK ) )
+       && RX_PRECOMP(old_re)
+       && RX_PRELEN(old_re) == plen
+        && memEQ(RX_PRECOMP(old_re), exp, plen)
+       && !runtime_code /* with runtime code, always recompile */ )
+    {
+        Safefree(pRExC_state->code_blocks);
+        return old_re;
+    }
+
+    rx_flags = orig_rx_flags;
+
+    if (rx_flags & PMf_FOLD) {
+        RExC_contains_i = 1;
+    }
+    if (RExC_utf8 && initial_charset == REGEX_DEPENDS_CHARSET) {
+
+       /* Set to use unicode semantics if the pattern is in utf8 and has the
+        * 'depends' charset specified, as it means unicode when utf8  */
+       set_regex_charset(&rx_flags, REGEX_UNICODE_CHARSET);
+    }
+
+    RExC_precomp = exp;
+    RExC_flags = rx_flags;
+    RExC_pm_flags = pm_flags;
+
+    if (runtime_code) {
+       if (TAINTING_get && TAINT_get)
+           Perl_croak(aTHX_ "Eval-group in insecure regular expression");
+
+       if (!S_compile_runtime_code(aTHX_ pRExC_state, exp, plen)) {
+           /* whoops, we have a non-utf8 pattern, whilst run-time code
+            * got compiled as utf8. Try again with a utf8 pattern */
+            S_pat_upgrade_to_utf8(aTHX_ pRExC_state, &exp, &plen,
+                                    pRExC_state->num_code_blocks);
+            goto redo_first_pass;
+       }
+    }
+    assert(!pRExC_state->runtime_code_qr);
+
+    RExC_sawback = 0;
+
+    RExC_seen = 0;
+    RExC_maxlen = 0;
+    RExC_in_lookbehind = 0;
+    RExC_seen_zerolen = *exp == '^' ? -1 : 0;
+    RExC_extralen = 0;
+    RExC_override_recoding = 0;
+    RExC_in_multi_char_class = 0;
+
+    /* First pass: determine size, legality. */
+    RExC_parse = exp;
+    RExC_start = exp;
+    RExC_end = exp + plen;
+    RExC_naughty = 0;
+    RExC_npar = 1;
+    RExC_nestroot = 0;
+    RExC_size = 0L;
+    RExC_emit = (regnode *) &RExC_emit_dummy;
+    RExC_whilem_seen = 0;
+    RExC_open_parens = NULL;
+    RExC_close_parens = NULL;
+    RExC_opend = NULL;
+    RExC_paren_names = NULL;
+#ifdef DEBUGGING
+    RExC_paren_name_list = NULL;
+#endif
+    RExC_recurse = NULL;
+    RExC_study_chunk_recursed = NULL;
+    RExC_study_chunk_recursed_bytes= 0;
+    RExC_recurse_count = 0;
+    pRExC_state->code_index = 0;
+
+#if 0 /* REGC() is (currently) a NOP at the first pass.
+       * Clever compilers notice this and complain. --jhi */
+    REGC((U8)REG_MAGIC, (char*)RExC_emit);
+#endif
+    DEBUG_PARSE_r(
+       PerlIO_printf(Perl_debug_log, "Starting first pass (sizing)\n");
+        RExC_lastnum=0;
+        RExC_lastparse=NULL;
+    );
+    /* reg may croak on us, not giving us a chance to free
+       pRExC_state->code_blocks.  We cannot SAVEFREEPV it now, as we may
+       need it to survive as long as the regexp (qr/(?{})/).
+       We must check that code_blocksv is not already set, because we may
+       have jumped back to restart the sizing pass. */
+    if (pRExC_state->code_blocks && !code_blocksv) {
+       code_blocksv = newSV_type(SVt_PV);
+       SAVEFREESV(code_blocksv);
+       SvPV_set(code_blocksv, (char *)pRExC_state->code_blocks);
+       SvLEN_set(code_blocksv, 1); /*sufficient to make sv_clear free it*/
+    }
+    if (reg(pRExC_state, 0, &flags,1) == NULL) {
+        /* It's possible to write a regexp in ascii that represents Unicode
+        codepoints outside of the byte range, such as via \x{100}. If we
+        detect such a sequence we have to convert the entire pattern to utf8
+        and then recompile, as our sizing calculation will have been based
+        on 1 byte == 1 character, but we will need to use utf8 to encode
+        at least some part of the pattern, and therefore must convert the whole
+        thing.
+        -- dmq */
+        if (flags & RESTART_UTF8) {
+            S_pat_upgrade_to_utf8(aTHX_ pRExC_state, &exp, &plen,
+                                    pRExC_state->num_code_blocks);
+            goto redo_first_pass;
+        }
+        Perl_croak(aTHX_ "panic: reg returned NULL to re_op_compile for sizing pass, flags=%#"UVxf"", (UV) flags);
+    }
+    if (code_blocksv)
+       SvLEN_set(code_blocksv,0); /* no you can't have it, sv_clear */
+
+    DEBUG_PARSE_r({
+        PerlIO_printf(Perl_debug_log,
+            "Required size %"IVdf" nodes\n"
+            "Starting second pass (creation)\n",
+            (IV)RExC_size);
+        RExC_lastnum=0;
+        RExC_lastparse=NULL;
+    });
+
+    /* The first pass could have found things that force Unicode semantics */
+    if ((RExC_utf8 || RExC_uni_semantics)
+        && get_regex_charset(rx_flags) == REGEX_DEPENDS_CHARSET)
+    {
+       set_regex_charset(&rx_flags, REGEX_UNICODE_CHARSET);
+    }
+
+    /* Small enough for pointer-storage convention?
+       If extralen==0, this means that we will not need long jumps. */
+    if (RExC_size >= 0x10000L && RExC_extralen)
+        RExC_size += RExC_extralen;
+    else
+       RExC_extralen = 0;
+    if (RExC_whilem_seen > 15)
+       RExC_whilem_seen = 15;
+
+    /* Allocate space and zero-initialize. Note, the two step process
+       of zeroing when in debug mode, thus anything assigned has to
+       happen after that */
+    rx = (REGEXP*) newSV_type(SVt_REGEXP);
+    r = ReANY(rx);
+    Newxc(ri, sizeof(regexp_internal) + (unsigned)RExC_size * sizeof(regnode),
+        char, regexp_internal);
+    if ( r == NULL || ri == NULL )
+       FAIL("Regexp out of space");
+#ifdef DEBUGGING
+    /* avoid reading uninitialized memory in DEBUGGING code in study_chunk() */
+    Zero(ri, sizeof(regexp_internal) + (unsigned)RExC_size * sizeof(regnode),
+         char);
+#else
+    /* bulk initialize base fields with 0. */
+    Zero(ri, sizeof(regexp_internal), char);
+#endif
+
+    /* non-zero initialization begins here */
+    RXi_SET( r, ri );
+    r->engine= eng;
+    r->extflags = rx_flags;
+    RXp_COMPFLAGS(r) = orig_rx_flags & RXf_PMf_FLAGCOPYMASK;
+
+    if (pm_flags & PMf_IS_QR) {
+       ri->code_blocks = pRExC_state->code_blocks;
+       ri->num_code_blocks = pRExC_state->num_code_blocks;
+    }
+    else
+    {
+       int n;
+       for (n = 0; n < pRExC_state->num_code_blocks; n++)
+           if (pRExC_state->code_blocks[n].src_regex)
+               SAVEFREESV(pRExC_state->code_blocks[n].src_regex);
+       SAVEFREEPV(pRExC_state->code_blocks);
+    }
+
+    {
+        bool has_p     = ((r->extflags & RXf_PMf_KEEPCOPY) == RXf_PMf_KEEPCOPY);
+        bool has_charset = (get_regex_charset(r->extflags)
+                                                    != REGEX_DEPENDS_CHARSET);
+
+        /* The caret is output if there are any defaults: if not all the STD
+         * flags are set, or if no character set specifier is needed */
+        bool has_default =
+                    (((r->extflags & RXf_PMf_STD_PMMOD) != RXf_PMf_STD_PMMOD)
+                    || ! has_charset);
+        bool has_runon = ((RExC_seen & REG_RUN_ON_COMMENT_SEEN)
+                                                   == REG_RUN_ON_COMMENT_SEEN);
+       U16 reganch = (U16)((r->extflags & RXf_PMf_STD_PMMOD)
+                           >> RXf_PMf_STD_PMMOD_SHIFT);
+       const char *fptr = STD_PAT_MODS;        /*"msix"*/
+       char *p;
+        /* Allocate for the worst case, which is all the std flags are turned
+         * on.  If more precision is desired, we could do a population count of
+         * the flags set.  This could be done with a small lookup table, or by
+         * shifting, masking and adding, or even, when available, assembly
+         * language for a machine-language population count.
+         * We never output a minus, as all those are defaults, so are
+         * covered by the caret */
+       const STRLEN wraplen = plen + has_p + has_runon
+            + has_default       /* If needs a caret */
+
+               /* If needs a character set specifier */
+           + ((has_charset) ? MAX_CHARSET_NAME_LENGTH : 0)
+            + (sizeof(STD_PAT_MODS) - 1)
+            + (sizeof("(?:)") - 1);
+
+        Newx(p, wraplen + 1, char); /* +1 for the ending NUL */
+       r->xpv_len_u.xpvlenu_pv = p;
+       if (RExC_utf8)
+           SvFLAGS(rx) |= SVf_UTF8;
+        *p++='('; *p++='?';
+
+        /* If a default, cover it using the caret */
+        if (has_default) {
+            *p++= DEFAULT_PAT_MOD;
+        }
+        if (has_charset) {
+           STRLEN len;
+           const char* const name = get_regex_charset_name(r->extflags, &len);
+           Copy(name, p, len, char);
+           p += len;
+        }
+        if (has_p)
+            *p++ = KEEPCOPY_PAT_MOD; /*'p'*/
+        {
+            char ch;
+            while((ch = *fptr++)) {
+                if(reganch & 1)
+                    *p++ = ch;
+                reganch >>= 1;
+            }
+        }
+
+        *p++ = ':';
+        Copy(RExC_precomp, p, plen, char);
+       assert ((RX_WRAPPED(rx) - p) < 16);
+       r->pre_prefix = p - RX_WRAPPED(rx);
+        p += plen;
+        if (has_runon)
+            *p++ = '\n';
+        *p++ = ')';
+        *p = 0;
+       SvCUR_set(rx, p - RX_WRAPPED(rx));
+    }
+
+    r->intflags = 0;
+    r->nparens = RExC_npar - 1;        /* set early to validate backrefs */
+
+    /* setup various meta data about recursion, this all requires
+     * RExC_npar to be correctly set, and a bit later on we clear it */
+    if (RExC_seen & REG_RECURSE_SEEN) {
+        Newxz(RExC_open_parens, RExC_npar,regnode *);
+        SAVEFREEPV(RExC_open_parens);
+        Newxz(RExC_close_parens,RExC_npar,regnode *);
+        SAVEFREEPV(RExC_close_parens);
+    }
+    if (RExC_seen & (REG_RECURSE_SEEN | REG_GOSTART_SEEN)) {
+        /* Note, RExC_npar is 1 + the number of parens in a pattern.
+         * So its 1 if there are no parens. */
+        RExC_study_chunk_recursed_bytes= (RExC_npar >> 3) +
+                                         ((RExC_npar & 0x07) != 0);
+        Newx(RExC_study_chunk_recursed,
+             RExC_study_chunk_recursed_bytes * RExC_npar, U8);
+        SAVEFREEPV(RExC_study_chunk_recursed);
+    }
+
+    /* Useful during FAIL. */
+#ifdef RE_TRACK_PATTERN_OFFSETS
+    Newxz(ri->u.offsets, 2*RExC_size+1, U32); /* MJD 20001228 */
+    DEBUG_OFFSETS_r(PerlIO_printf(Perl_debug_log,
+                          "%s %"UVuf" bytes for offset annotations.\n",
+                          ri->u.offsets ? "Got" : "Couldn't get",
+                          (UV)((2*RExC_size+1) * sizeof(U32))));
+#endif
+    SetProgLen(ri,RExC_size);
+    RExC_rx_sv = rx;
+    RExC_rx = r;
+    RExC_rxi = ri;
+
+    /* Second pass: emit code. */
+    RExC_flags = rx_flags;     /* don't let top level (?i) bleed */
+    RExC_pm_flags = pm_flags;
+    RExC_parse = exp;
+    RExC_end = exp + plen;
+    RExC_naughty = 0;
+    RExC_npar = 1;
+    RExC_emit_start = ri->program;
+    RExC_emit = ri->program;
+    RExC_emit_bound = ri->program + RExC_size + 1;
+    pRExC_state->code_index = 0;
+
+    REGC((U8)REG_MAGIC, (char*) RExC_emit++);
+    if (reg(pRExC_state, 0, &flags,1) == NULL) {
+       ReREFCNT_dec(rx);
+        Perl_croak(aTHX_ "panic: reg returned NULL to re_op_compile for generation pass, flags=%#"UVxf"", (UV) flags);
+    }
+    /* XXXX To minimize changes to RE engine we always allocate
+       3-units-long substrs field. */
+    Newx(r->substrs, 1, struct reg_substr_data);
+    if (RExC_recurse_count) {
+        Newxz(RExC_recurse,RExC_recurse_count,regnode *);
+        SAVEFREEPV(RExC_recurse);
+    }
+
+reStudy:
+    r->minlen = minlen = sawlookahead = sawplus = sawopen = sawminmod = 0;
+    Zero(r->substrs, 1, struct reg_substr_data);
+    if (RExC_study_chunk_recursed)
+        Zero(RExC_study_chunk_recursed,
+             RExC_study_chunk_recursed_bytes * RExC_npar, U8);
+
+#ifdef TRIE_STUDY_OPT
+    if (!restudied) {
+        StructCopy(&zero_scan_data, &data, scan_data_t);
+        copyRExC_state = RExC_state;
+    } else {
+        U32 seen=RExC_seen;
+        DEBUG_OPTIMISE_r(PerlIO_printf(Perl_debug_log,"Restudying\n"));
+
+        RExC_state = copyRExC_state;
+        if (seen & REG_TOP_LEVEL_BRANCHES_SEEN)
+            RExC_seen |= REG_TOP_LEVEL_BRANCHES_SEEN;
+        else
+            RExC_seen &= ~REG_TOP_LEVEL_BRANCHES_SEEN;
+       StructCopy(&zero_scan_data, &data, scan_data_t);
+    }
+#else
+    StructCopy(&zero_scan_data, &data, scan_data_t);
+#endif
+
+    /* Dig out information for optimizations. */
+    r->extflags = RExC_flags; /* was pm_op */
+    /*dmq: removed as part of de-PMOP: pm->op_pmflags = RExC_flags; */
+
+    if (UTF)
+       SvUTF8_on(rx);  /* Unicode in it? */
+    ri->regstclass = NULL;
+    if (RExC_naughty >= 10)    /* Probably an expensive pattern. */
+       r->intflags |= PREGf_NAUGHTY;
+    scan = ri->program + 1;            /* First BRANCH. */
+
+    /* testing for BRANCH here tells us whether there is "must appear"
+       data in the pattern. If there is then we can use it for optimisations */
+    if (!(RExC_seen & REG_TOP_LEVEL_BRANCHES_SEEN)) { /*  Only one top-level choice.
+                                                  */
+       SSize_t fake;
+       STRLEN longest_float_length, longest_fixed_length;
+       regnode_ssc ch_class; /* pointed to by data */
+       int stclass_flag;
+       SSize_t last_close = 0; /* pointed to by data */
+        regnode *first= scan;
+        regnode *first_next= regnext(first);
+       /*
+        * Skip introductions and multiplicators >= 1
+        * so that we can extract the 'meat' of the pattern that must
+        * match in the large if() sequence following.
+        * NOTE that EXACT is NOT covered here, as it is normally
+        * picked up by the optimiser separately.
+        *
+        * This is unfortunate as the optimiser isnt handling lookahead
+        * properly currently.
+        *
+        */
+       while ((OP(first) == OPEN && (sawopen = 1)) ||
+              /* An OR of *one* alternative - should not happen now. */
+           (OP(first) == BRANCH && OP(first_next) != BRANCH) ||
+           /* for now we can't handle lookbehind IFMATCH*/
+           (OP(first) == IFMATCH && !first->flags && (sawlookahead = 1)) ||
+           (OP(first) == PLUS) ||
+           (OP(first) == MINMOD) ||
+              /* An {n,m} with n>0 */
+           (PL_regkind[OP(first)] == CURLY && ARG1(first) > 0) ||
+           (OP(first) == NOTHING && PL_regkind[OP(first_next)] != END ))
+       {
+               /*
+                * the only op that could be a regnode is PLUS, all the rest
+                * will be regnode_1 or regnode_2.
+                *
+                 * (yves doesn't think this is true)
+                */
+               if (OP(first) == PLUS)
+                   sawplus = 1;
+                else {
+                    if (OP(first) == MINMOD)
+                        sawminmod = 1;
+                   first += regarglen[OP(first)];
+                }
+               first = NEXTOPER(first);
+               first_next= regnext(first);
+       }
+
+       /* Starting-point info. */
+      again:
+        DEBUG_PEEP("first:",first,0);
+        /* Ignore EXACT as we deal with it later. */
+       if (PL_regkind[OP(first)] == EXACT) {
+           if (OP(first) == EXACT)
+               NOOP;   /* Empty, get anchored substr later. */
+           else
+               ri->regstclass = first;
+       }
+#ifdef TRIE_STCLASS
+       else if (PL_regkind[OP(first)] == TRIE &&
+               ((reg_trie_data *)ri->data->data[ ARG(first) ])->minlen>0)
+       {
+           regnode *trie_op;
+           /* this can happen only on restudy */
+           if ( OP(first) == TRIE ) {
+                struct regnode_1 *trieop = (struct regnode_1 *)
+                   PerlMemShared_calloc(1, sizeof(struct regnode_1));
+                StructCopy(first,trieop,struct regnode_1);
+                trie_op=(regnode *)trieop;
+            } else {
+                struct regnode_charclass *trieop = (struct regnode_charclass *)
+                   PerlMemShared_calloc(1, sizeof(struct regnode_charclass));
+                StructCopy(first,trieop,struct regnode_charclass);
+                trie_op=(regnode *)trieop;
+            }
+            OP(trie_op)+=2;
+            make_trie_failtable(pRExC_state, (regnode *)first, trie_op, 0);
+           ri->regstclass = trie_op;
+       }
+#endif
+       else if (REGNODE_SIMPLE(OP(first)))
+           ri->regstclass = first;
+       else if (PL_regkind[OP(first)] == BOUND ||
+                PL_regkind[OP(first)] == NBOUND)
+           ri->regstclass = first;
+       else if (PL_regkind[OP(first)] == BOL) {
+            r->intflags |= (OP(first) == MBOL
+                           ? PREGf_ANCH_MBOL
+                          : (OP(first) == SBOL
+                              ? PREGf_ANCH_SBOL
+                              : PREGf_ANCH_BOL));
+           first = NEXTOPER(first);
+           goto again;
+       }
+       else if (OP(first) == GPOS) {
+            r->intflags |= PREGf_ANCH_GPOS;
+           first = NEXTOPER(first);
+           goto again;
+       }
+       else if ((!sawopen || !RExC_sawback) &&
+           (OP(first) == STAR &&
+           PL_regkind[OP(NEXTOPER(first))] == REG_ANY) &&
+            !(r->intflags & PREGf_ANCH) && !pRExC_state->num_code_blocks)
+       {
+           /* turn .* into ^.* with an implied $*=1 */
+           const int type =
+               (OP(NEXTOPER(first)) == REG_ANY)
+                    ? PREGf_ANCH_MBOL
+                    : PREGf_ANCH_SBOL;
+            r->intflags |= (type | PREGf_IMPLICIT);
+           first = NEXTOPER(first);
+           goto again;
+       }
+        if (sawplus && !sawminmod && !sawlookahead
+            && (!sawopen || !RExC_sawback)
+           && !pRExC_state->num_code_blocks) /* May examine pos and $& */
+           /* x+ must match at the 1st pos of run of x's */
+           r->intflags |= PREGf_SKIP;
+
+       /* Scan is after the zeroth branch, first is atomic matcher. */
+#ifdef TRIE_STUDY_OPT
+       DEBUG_PARSE_r(
+           if (!restudied)
+               PerlIO_printf(Perl_debug_log, "first at %"IVdf"\n",
+                             (IV)(first - scan + 1))
+        );
+#else
+       DEBUG_PARSE_r(
+           PerlIO_printf(Perl_debug_log, "first at %"IVdf"\n",
+               (IV)(first - scan + 1))
+        );
+#endif
+
+
+       /*
+       * If there's something expensive in the r.e., find the
+       * longest literal string that must appear and make it the
+       * regmust.  Resolve ties in favor of later strings, since
+       * the regstart check works with the beginning of the r.e.
+       * and avoiding duplication strengthens checking.  Not a
+       * strong reason, but sufficient in the absence of others.
+       * [Now we resolve ties in favor of the earlier string if
+       * it happens that c_offset_min has been invalidated, since the
+       * earlier string may buy us something the later one won't.]
+       */
+
+       data.longest_fixed = newSVpvs("");
+       data.longest_float = newSVpvs("");
+       data.last_found = newSVpvs("");
+       data.longest = &(data.longest_fixed);
+       ENTER_with_name("study_chunk");
+       SAVEFREESV(data.longest_fixed);
+       SAVEFREESV(data.longest_float);
+       SAVEFREESV(data.last_found);
+       first = scan;
+       if (!ri->regstclass) {
+           ssc_init(pRExC_state, &ch_class);
+           data.start_class = &ch_class;
+           stclass_flag = SCF_DO_STCLASS_AND;
+       } else                          /* XXXX Check for BOUND? */
+           stclass_flag = 0;
+       data.last_closep = &last_close;
+
+        DEBUG_RExC_seen();
+       minlen = study_chunk(pRExC_state, &first, &minlen, &fake,
+                             scan + RExC_size, /* Up to end */
+            &data, -1, 0, NULL,
+            SCF_DO_SUBSTR | SCF_WHILEM_VISITED_POS | stclass_flag
+                          | (restudied ? SCF_TRIE_DOING_RESTUDY : 0),
+            0);
+
+
+        CHECK_RESTUDY_GOTO_butfirst(LEAVE_with_name("study_chunk"));
+
+
+       if ( RExC_npar == 1 && data.longest == &(data.longest_fixed)
+            && data.last_start_min == 0 && data.last_end > 0
+            && !RExC_seen_zerolen
+             && !(RExC_seen & REG_VERBARG_SEEN)
+             && !(RExC_seen & REG_GPOS_SEEN)
+        ){
+           r->extflags |= RXf_CHECK_ALL;
+        }
+       scan_commit(pRExC_state, &data,&minlen,0);
+
+       longest_float_length = CHR_SVLEN(data.longest_float);
+
+        if (! ((SvCUR(data.longest_fixed)  /* ok to leave SvCUR */
+                   && data.offset_fixed == data.offset_float_min
+                   && SvCUR(data.longest_fixed) == SvCUR(data.longest_float)))
+            && S_setup_longest (aTHX_ pRExC_state,
+                                    data.longest_float,
+                                    &(r->float_utf8),
+                                    &(r->float_substr),
+                                    &(r->float_end_shift),
+                                    data.lookbehind_float,
+                                    data.offset_float_min,
+                                    data.minlen_float,
+                                    longest_float_length,
+                                    cBOOL(data.flags & SF_FL_BEFORE_EOL),
+                                    cBOOL(data.flags & SF_FL_BEFORE_MEOL)))
+        {
+           r->float_min_offset = data.offset_float_min - data.lookbehind_float;
+           r->float_max_offset = data.offset_float_max;
+           if (data.offset_float_max < SSize_t_MAX) /* Don't offset infinity */
+               r->float_max_offset -= data.lookbehind_float;
+           SvREFCNT_inc_simple_void_NN(data.longest_float);
+       }
+       else {
+           r->float_substr = r->float_utf8 = NULL;
+           longest_float_length = 0;
+       }
+
+       longest_fixed_length = CHR_SVLEN(data.longest_fixed);
+
+        if (S_setup_longest (aTHX_ pRExC_state,
+                                data.longest_fixed,
+                                &(r->anchored_utf8),
+                                &(r->anchored_substr),
+                                &(r->anchored_end_shift),
+                                data.lookbehind_fixed,
+                                data.offset_fixed,
+                                data.minlen_fixed,
+                                longest_fixed_length,
+                                cBOOL(data.flags & SF_FIX_BEFORE_EOL),
+                                cBOOL(data.flags & SF_FIX_BEFORE_MEOL)))
+        {
+           r->anchored_offset = data.offset_fixed - data.lookbehind_fixed;
+           SvREFCNT_inc_simple_void_NN(data.longest_fixed);
+       }
+       else {
+           r->anchored_substr = r->anchored_utf8 = NULL;
+           longest_fixed_length = 0;
+       }
+       LEAVE_with_name("study_chunk");
+
+       if (ri->regstclass
+           && (OP(ri->regstclass) == REG_ANY || OP(ri->regstclass) == SANY))
+           ri->regstclass = NULL;
+
+       if ((!(r->anchored_substr || r->anchored_utf8) || r->anchored_offset)
+           && stclass_flag
+            && ! (ANYOF_FLAGS(data.start_class) & ANYOF_EMPTY_STRING)
+           && !ssc_is_anything(data.start_class))
+       {
+           const U32 n = add_data(pRExC_state, STR_WITH_LEN("f"));
+
+            ssc_finalize(pRExC_state, data.start_class);
+
+           Newx(RExC_rxi->data->data[n], 1, regnode_ssc);
+           StructCopy(data.start_class,
+                      (regnode_ssc*)RExC_rxi->data->data[n],
+                      regnode_ssc);
+           ri->regstclass = (regnode*)RExC_rxi->data->data[n];
+           r->intflags &= ~PREGf_SKIP; /* Used in find_byclass(). */
+           DEBUG_COMPILE_r({ SV *sv = sv_newmortal();
+                     regprop(r, sv, (regnode*)data.start_class, NULL);
+                     PerlIO_printf(Perl_debug_log,
+                                   "synthetic stclass \"%s\".\n",
+                                   SvPVX_const(sv));});
+            data.start_class = NULL;
+       }
+
+        /* A temporary algorithm prefers floated substr to fixed one to dig
+         * more info. */
+       if (longest_fixed_length > longest_float_length) {
+           r->substrs->check_ix = 0;
+           r->check_end_shift = r->anchored_end_shift;
+           r->check_substr = r->anchored_substr;
+           r->check_utf8 = r->anchored_utf8;
+           r->check_offset_min = r->check_offset_max = r->anchored_offset;
+            if (r->intflags & (PREGf_ANCH_SBOL|PREGf_ANCH_GPOS))
+                r->intflags |= PREGf_NOSCAN;
+       }
+       else {
+           r->substrs->check_ix = 1;
+           r->check_end_shift = r->float_end_shift;
+           r->check_substr = r->float_substr;
+           r->check_utf8 = r->float_utf8;
+           r->check_offset_min = r->float_min_offset;
+           r->check_offset_max = r->float_max_offset;
+       }
+       if ((r->check_substr || r->check_utf8) ) {
+           r->extflags |= RXf_USE_INTUIT;
+           if (SvTAIL(r->check_substr ? r->check_substr : r->check_utf8))
+               r->extflags |= RXf_INTUIT_TAIL;
+       }
+        r->substrs->data[0].max_offset = r->substrs->data[0].min_offset;
+
+       /* XXX Unneeded? dmq (shouldn't as this is handled elsewhere)
+       if ( (STRLEN)minlen < longest_float_length )
+            minlen= longest_float_length;
+        if ( (STRLEN)minlen < longest_fixed_length )
+            minlen= longest_fixed_length;
+        */
+    }
+    else {
+       /* Several toplevels. Best we can is to set minlen. */
+       SSize_t fake;
+       regnode_ssc ch_class;
+       SSize_t last_close = 0;
+
+       DEBUG_PARSE_r(PerlIO_printf(Perl_debug_log, "\nMulti Top Level\n"));
+
+       scan = ri->program + 1;
+       ssc_init(pRExC_state, &ch_class);
+       data.start_class = &ch_class;
+       data.last_closep = &last_close;
+
+        DEBUG_RExC_seen();
+       minlen = study_chunk(pRExC_state,
+            &scan, &minlen, &fake, scan + RExC_size, &data, -1, 0, NULL,
+            SCF_DO_STCLASS_AND|SCF_WHILEM_VISITED_POS|(restudied
+                                                      ? SCF_TRIE_DOING_RESTUDY
+                                                      : 0),
+            0);
+
+        CHECK_RESTUDY_GOTO_butfirst(NOOP);
+
+       r->check_substr = r->check_utf8 = r->anchored_substr = r->anchored_utf8
+               = r->float_substr = r->float_utf8 = NULL;
+
+        if (! (ANYOF_FLAGS(data.start_class) & ANYOF_EMPTY_STRING)
+            && ! ssc_is_anything(data.start_class))
+        {
+           const U32 n = add_data(pRExC_state, STR_WITH_LEN("f"));
+
+            ssc_finalize(pRExC_state, data.start_class);
+
+           Newx(RExC_rxi->data->data[n], 1, regnode_ssc);
+           StructCopy(data.start_class,
+                      (regnode_ssc*)RExC_rxi->data->data[n],
+                      regnode_ssc);
+           ri->regstclass = (regnode*)RExC_rxi->data->data[n];
+           r->intflags &= ~PREGf_SKIP; /* Used in find_byclass(). */
+           DEBUG_COMPILE_r({ SV* sv = sv_newmortal();
+                     regprop(r, sv, (regnode*)data.start_class, NULL);
+                     PerlIO_printf(Perl_debug_log,
+                                   "synthetic stclass \"%s\".\n",
+                                   SvPVX_const(sv));});
+            data.start_class = NULL;
+       }
+    }
+
+    if (RExC_seen & REG_UNBOUNDED_QUANTIFIER_SEEN) {
+        r->extflags |= RXf_UNBOUNDED_QUANTIFIER_SEEN;
+        r->maxlen = REG_INFTY;
+    }
+    else {
+        r->maxlen = RExC_maxlen;
+    }
+
+    /* Guard against an embedded (?=) or (?<=) with a longer minlen than
+       the "real" pattern. */
+    DEBUG_OPTIMISE_r({
+        PerlIO_printf(Perl_debug_log,"minlen: %"IVdf" r->minlen:%"IVdf" maxlen:%ld\n",
+                      (IV)minlen, (IV)r->minlen, RExC_maxlen);
+    });
+    r->minlenret = minlen;
+    if (r->minlen < minlen)
+        r->minlen = minlen;
+
+    if (RExC_seen & REG_GPOS_SEEN)
+        r->intflags |= PREGf_GPOS_SEEN;
+    if (RExC_seen & REG_LOOKBEHIND_SEEN)
+        r->extflags |= RXf_NO_INPLACE_SUBST; /* inplace might break the
+                                                lookbehind */
+    if (pRExC_state->num_code_blocks)
+       r->extflags |= RXf_EVAL_SEEN;
+    if (RExC_seen & REG_CANY_SEEN)
+        r->intflags |= PREGf_CANY_SEEN;
+    if (RExC_seen & REG_VERBARG_SEEN)
+    {
+       r->intflags |= PREGf_VERBARG_SEEN;
+        r->extflags |= RXf_NO_INPLACE_SUBST; /* don't understand this! Yves */
+    }
+    if (RExC_seen & REG_CUTGROUP_SEEN)
+       r->intflags |= PREGf_CUTGROUP_SEEN;
+    if (pm_flags & PMf_USE_RE_EVAL)
+       r->intflags |= PREGf_USE_RE_EVAL;
+    if (RExC_paren_names)
+        RXp_PAREN_NAMES(r) = MUTABLE_HV(SvREFCNT_inc(RExC_paren_names));
+    else
+        RXp_PAREN_NAMES(r) = NULL;
+
+    /* If we have seen an anchor in our pattern then we set the extflag RXf_IS_ANCHORED
+     * so it can be used in pp.c */
+    if (r->intflags & PREGf_ANCH)
+        r->extflags |= RXf_IS_ANCHORED;
+
+
+    {
+        /* this is used to identify "special" patterns that might result
+         * in Perl NOT calling the regex engine and instead doing the match "itself",
+         * particularly special cases in split//. By having the regex compiler
+         * do this pattern matching at a regop level (instead of by inspecting the pattern)
+         * we avoid weird issues with equivalent patterns resulting in different behavior,
+         * AND we allow non Perl engines to get the same optimizations by the setting the
+         * flags appropriately - Yves */
+        regnode *first = ri->program + 1;
+        U8 fop = OP(first);
+        regnode *next = NEXTOPER(first);
+        U8 nop = OP(next);
+
+        if (PL_regkind[fop] == NOTHING && nop == END)
+            r->extflags |= RXf_NULL;
+        else if (PL_regkind[fop] == BOL && nop == END)
+            r->extflags |= RXf_START_ONLY;
+        else if (fop == PLUS
+                 && PL_regkind[nop] == POSIXD && FLAGS(next) == _CC_SPACE
+                 && OP(regnext(first)) == END)
+            r->extflags |= RXf_WHITE;
+        else if ( r->extflags & RXf_SPLIT
+                  && fop == EXACT
+                  && STR_LEN(first) == 1
+                  && *(STRING(first)) == ' '
+                  && OP(regnext(first)) == END )
+            r->extflags |= (RXf_SKIPWHITE|RXf_WHITE);
+
+    }
+
+    if (RExC_contains_locale) {
+        RXp_EXTFLAGS(r) |= RXf_TAINTED;
+    }
+
+#ifdef DEBUGGING
+    if (RExC_paren_names) {
+        ri->name_list_idx = add_data( pRExC_state, STR_WITH_LEN("a"));
+        ri->data->data[ri->name_list_idx]
+                                   = (void*)SvREFCNT_inc(RExC_paren_name_list);
+    } else
+#endif
+        ri->name_list_idx = 0;
+
+    if (RExC_recurse_count) {
+        for ( ; RExC_recurse_count ; RExC_recurse_count-- ) {
+            const regnode *scan = RExC_recurse[RExC_recurse_count-1];
+            ARG2L_SET( scan, RExC_open_parens[ARG(scan)-1] - scan );
+        }
+    }
+    Newxz(r->offs, RExC_npar, regexp_paren_pair);
+    /* assume we don't need to swap parens around before we match */
+
+    DEBUG_DUMP_r({
+        DEBUG_RExC_seen();
+        PerlIO_printf(Perl_debug_log,"Final program:\n");
+        regdump(r);
+    });
+#ifdef RE_TRACK_PATTERN_OFFSETS
+    DEBUG_OFFSETS_r(if (ri->u.offsets) {
+        const STRLEN len = ri->u.offsets[0];
+        STRLEN i;
+        GET_RE_DEBUG_FLAGS_DECL;
+        PerlIO_printf(Perl_debug_log,
+                      "Offsets: [%"UVuf"]\n\t", (UV)ri->u.offsets[0]);
+        for (i = 1; i <= len; i++) {
+            if (ri->u.offsets[i*2-1] || ri->u.offsets[i*2])
+                PerlIO_printf(Perl_debug_log, "%"UVuf":%"UVuf"[%"UVuf"] ",
+                (UV)i, (UV)ri->u.offsets[i*2-1], (UV)ri->u.offsets[i*2]);
+            }
+        PerlIO_printf(Perl_debug_log, "\n");
+    });
+#endif
+
+#ifdef USE_ITHREADS
+    /* under ithreads the ?pat? PMf_USED flag on the pmop is simulated
+     * by setting the regexp SV to readonly-only instead. If the
+     * pattern's been recompiled, the USEDness should remain. */
+    if (old_re && SvREADONLY(old_re))
+        SvREADONLY_on(rx);
+#endif
+    return rx;
+}
+
+
+SV*
+Perl_reg_named_buff(pTHX_ REGEXP * const rx, SV * const key, SV * const value,
+                    const U32 flags)
+{
+    PERL_ARGS_ASSERT_REG_NAMED_BUFF;
+
+    PERL_UNUSED_ARG(value);
+
+    if (flags & RXapif_FETCH) {
+        return reg_named_buff_fetch(rx, key, flags);
+    } else if (flags & (RXapif_STORE | RXapif_DELETE | RXapif_CLEAR)) {
+        Perl_croak_no_modify();
+        return NULL;
+    } else if (flags & RXapif_EXISTS) {
+        return reg_named_buff_exists(rx, key, flags)
+            ? &PL_sv_yes
+            : &PL_sv_no;
+    } else if (flags & RXapif_REGNAMES) {
+        return reg_named_buff_all(rx, flags);
+    } else if (flags & (RXapif_SCALAR | RXapif_REGNAMES_COUNT)) {
+        return reg_named_buff_scalar(rx, flags);
+    } else {
+        Perl_croak(aTHX_ "panic: Unknown flags %d in named_buff", (int)flags);
+        return NULL;
+    }
+}
+
+SV*
+Perl_reg_named_buff_iter(pTHX_ REGEXP * const rx, const SV * const lastkey,
+                         const U32 flags)
+{
+    PERL_ARGS_ASSERT_REG_NAMED_BUFF_ITER;
+    PERL_UNUSED_ARG(lastkey);
+
+    if (flags & RXapif_FIRSTKEY)
+        return reg_named_buff_firstkey(rx, flags);
+    else if (flags & RXapif_NEXTKEY)
+        return reg_named_buff_nextkey(rx, flags);
+    else {
+        Perl_croak(aTHX_ "panic: Unknown flags %d in named_buff_iter",
+                                            (int)flags);
+        return NULL;
+    }
+}
+
+SV*
+Perl_reg_named_buff_fetch(pTHX_ REGEXP * const r, SV * const namesv,
+                         const U32 flags)
+{
+    AV *retarray = NULL;
+    SV *ret;
+    struct regexp *const rx = ReANY(r);
+
+    PERL_ARGS_ASSERT_REG_NAMED_BUFF_FETCH;
+
+    if (flags & RXapif_ALL)
+        retarray=newAV();
+
+    if (rx && RXp_PAREN_NAMES(rx)) {
+        HE *he_str = hv_fetch_ent( RXp_PAREN_NAMES(rx), namesv, 0, 0 );
+        if (he_str) {
+            IV i;
+            SV* sv_dat=HeVAL(he_str);
+            I32 *nums=(I32*)SvPVX(sv_dat);
+            for ( i=0; i<SvIVX(sv_dat); i++ ) {
+                if ((I32)(rx->nparens) >= nums[i]
+                    && rx->offs[nums[i]].start != -1
+                    && rx->offs[nums[i]].end != -1)
+                {
+                    ret = newSVpvs("");
+                    CALLREG_NUMBUF_FETCH(r,nums[i],ret);
+                    if (!retarray)
+                        return ret;
+                } else {
+                    if (retarray)
+                        ret = newSVsv(&PL_sv_undef);
+                }
+                if (retarray)
+                    av_push(retarray, ret);
+            }
+            if (retarray)
+                return newRV_noinc(MUTABLE_SV(retarray));
+        }
+    }
+    return NULL;
+}
+
+bool
+Perl_reg_named_buff_exists(pTHX_ REGEXP * const r, SV * const key,
+                           const U32 flags)
+{
+    struct regexp *const rx = ReANY(r);
+
+    PERL_ARGS_ASSERT_REG_NAMED_BUFF_EXISTS;
+
+    if (rx && RXp_PAREN_NAMES(rx)) {
+        if (flags & RXapif_ALL) {
+            return hv_exists_ent(RXp_PAREN_NAMES(rx), key, 0);
+        } else {
+           SV *sv = CALLREG_NAMED_BUFF_FETCH(r, key, flags);
+            if (sv) {
+               SvREFCNT_dec_NN(sv);
+                return TRUE;
+            } else {
+                return FALSE;
+            }
+        }
+    } else {
+        return FALSE;
+    }
+}
+
+SV*
+Perl_reg_named_buff_firstkey(pTHX_ REGEXP * const r, const U32 flags)
+{
+    struct regexp *const rx = ReANY(r);
+
+    PERL_ARGS_ASSERT_REG_NAMED_BUFF_FIRSTKEY;
+
+    if ( rx && RXp_PAREN_NAMES(rx) ) {
+       (void)hv_iterinit(RXp_PAREN_NAMES(rx));
+
+       return CALLREG_NAMED_BUFF_NEXTKEY(r, NULL, flags & ~RXapif_FIRSTKEY);
+    } else {
+       return FALSE;
+    }
+}
+
+SV*
+Perl_reg_named_buff_nextkey(pTHX_ REGEXP * const r, const U32 flags)
+{
+    struct regexp *const rx = ReANY(r);
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REG_NAMED_BUFF_NEXTKEY;
+
+    if (rx && RXp_PAREN_NAMES(rx)) {
+        HV *hv = RXp_PAREN_NAMES(rx);
+        HE *temphe;
+        while ( (temphe = hv_iternext_flags(hv,0)) ) {
+            IV i;
+            IV parno = 0;
+            SV* sv_dat = HeVAL(temphe);
+            I32 *nums = (I32*)SvPVX(sv_dat);
+            for ( i = 0; i < SvIVX(sv_dat); i++ ) {
+                if ((I32)(rx->lastparen) >= nums[i] &&
+                    rx->offs[nums[i]].start != -1 &&
+                    rx->offs[nums[i]].end != -1)
+                {
+                    parno = nums[i];
+                    break;
+                }
+            }
+            if (parno || flags & RXapif_ALL) {
+               return newSVhek(HeKEY_hek(temphe));
+            }
+        }
+    }
+    return NULL;
+}
+
+SV*
+Perl_reg_named_buff_scalar(pTHX_ REGEXP * const r, const U32 flags)
+{
+    SV *ret;
+    AV *av;
+    SSize_t length;
+    struct regexp *const rx = ReANY(r);
+
+    PERL_ARGS_ASSERT_REG_NAMED_BUFF_SCALAR;
+
+    if (rx && RXp_PAREN_NAMES(rx)) {
+        if (flags & (RXapif_ALL | RXapif_REGNAMES_COUNT)) {
+            return newSViv(HvTOTALKEYS(RXp_PAREN_NAMES(rx)));
+        } else if (flags & RXapif_ONE) {
+            ret = CALLREG_NAMED_BUFF_ALL(r, (flags | RXapif_REGNAMES));
+            av = MUTABLE_AV(SvRV(ret));
+            length = av_tindex(av);
+           SvREFCNT_dec_NN(ret);
+            return newSViv(length + 1);
+        } else {
+            Perl_croak(aTHX_ "panic: Unknown flags %d in named_buff_scalar",
+                                                (int)flags);
+            return NULL;
+        }
+    }
+    return &PL_sv_undef;
+}
+
+SV*
+Perl_reg_named_buff_all(pTHX_ REGEXP * const r, const U32 flags)
+{
+    struct regexp *const rx = ReANY(r);
+    AV *av = newAV();
+
+    PERL_ARGS_ASSERT_REG_NAMED_BUFF_ALL;
+
+    if (rx && RXp_PAREN_NAMES(rx)) {
+        HV *hv= RXp_PAREN_NAMES(rx);
+        HE *temphe;
+        (void)hv_iterinit(hv);
+        while ( (temphe = hv_iternext_flags(hv,0)) ) {
+            IV i;
+            IV parno = 0;
+            SV* sv_dat = HeVAL(temphe);
+            I32 *nums = (I32*)SvPVX(sv_dat);
+            for ( i = 0; i < SvIVX(sv_dat); i++ ) {
+                if ((I32)(rx->lastparen) >= nums[i] &&
+                    rx->offs[nums[i]].start != -1 &&
+                    rx->offs[nums[i]].end != -1)
+                {
+                    parno = nums[i];
+                    break;
+                }
+            }
+            if (parno || flags & RXapif_ALL) {
+                av_push(av, newSVhek(HeKEY_hek(temphe)));
+            }
+        }
+    }
+
+    return newRV_noinc(MUTABLE_SV(av));
+}
+
+void
+Perl_reg_numbered_buff_fetch(pTHX_ REGEXP * const r, const I32 paren,
+                            SV * const sv)
+{
+    struct regexp *const rx = ReANY(r);
+    char *s = NULL;
+    SSize_t i = 0;
+    SSize_t s1, t1;
+    I32 n = paren;
+
+    PERL_ARGS_ASSERT_REG_NUMBERED_BUFF_FETCH;
+
+    if (      n == RX_BUFF_IDX_CARET_PREMATCH
+           || n == RX_BUFF_IDX_CARET_FULLMATCH
+           || n == RX_BUFF_IDX_CARET_POSTMATCH
+       )
+    {
+        bool keepcopy = cBOOL(rx->extflags & RXf_PMf_KEEPCOPY);
+        if (!keepcopy) {
+            /* on something like
+             *    $r = qr/.../;
+             *    /$qr/p;
+             * the KEEPCOPY is set on the PMOP rather than the regex */
+            if (PL_curpm && r == PM_GETRE(PL_curpm))
+                 keepcopy = cBOOL(PL_curpm->op_pmflags & PMf_KEEPCOPY);
+        }
+        if (!keepcopy)
+            goto ret_undef;
+    }
+
+    if (!rx->subbeg)
+        goto ret_undef;
+
+    if (n == RX_BUFF_IDX_CARET_FULLMATCH)
+        /* no need to distinguish between them any more */
+        n = RX_BUFF_IDX_FULLMATCH;
+
+    if ((n == RX_BUFF_IDX_PREMATCH || n == RX_BUFF_IDX_CARET_PREMATCH)
+        && rx->offs[0].start != -1)
+    {
+        /* $`, ${^PREMATCH} */
+       i = rx->offs[0].start;
+       s = rx->subbeg;
+    }
+    else
+    if ((n == RX_BUFF_IDX_POSTMATCH || n == RX_BUFF_IDX_CARET_POSTMATCH)
+        && rx->offs[0].end != -1)
+    {
+        /* $', ${^POSTMATCH} */
+       s = rx->subbeg - rx->suboffset + rx->offs[0].end;
+       i = rx->sublen + rx->suboffset - rx->offs[0].end;
+    }
+    else
+    if ( 0 <= n && n <= (I32)rx->nparens &&
+        (s1 = rx->offs[n].start) != -1 &&
+        (t1 = rx->offs[n].end) != -1)
+    {
+        /* $&, ${^MATCH},  $1 ... */
+        i = t1 - s1;
+        s = rx->subbeg + s1 - rx->suboffset;
+    } else {
+        goto ret_undef;
+    }
+
+    assert(s >= rx->subbeg);
+    assert((STRLEN)rx->sublen >= (STRLEN)((s - rx->subbeg) + i) );
+    if (i >= 0) {
+#ifdef NO_TAINT_SUPPORT
+        sv_setpvn(sv, s, i);
+#else
+        const int oldtainted = TAINT_get;
+        TAINT_NOT;
+        sv_setpvn(sv, s, i);
+        TAINT_set(oldtainted);
+#endif
+        if ( (rx->intflags & PREGf_CANY_SEEN)
+            ? (RXp_MATCH_UTF8(rx)
+                        && (!i || is_utf8_string((U8*)s, i)))
+            : (RXp_MATCH_UTF8(rx)) )
+        {
+            SvUTF8_on(sv);
+        }
+        else
+            SvUTF8_off(sv);
+        if (TAINTING_get) {
+            if (RXp_MATCH_TAINTED(rx)) {
+                if (SvTYPE(sv) >= SVt_PVMG) {
+                    MAGIC* const mg = SvMAGIC(sv);
+                    MAGIC* mgt;
+                    TAINT;
+                    SvMAGIC_set(sv, mg->mg_moremagic);
+                    SvTAINT(sv);
+                    if ((mgt = SvMAGIC(sv))) {
+                        mg->mg_moremagic = mgt;
+                        SvMAGIC_set(sv, mg);
+                    }
+                } else {
+                    TAINT;
+                    SvTAINT(sv);
+                }
+            } else
+                SvTAINTED_off(sv);
+        }
+    } else {
+      ret_undef:
+        sv_setsv(sv,&PL_sv_undef);
+        return;
+    }
+}
+
+void
+Perl_reg_numbered_buff_store(pTHX_ REGEXP * const rx, const I32 paren,
+                                                        SV const * const value)
+{
+    PERL_ARGS_ASSERT_REG_NUMBERED_BUFF_STORE;
+
+    PERL_UNUSED_ARG(rx);
+    PERL_UNUSED_ARG(paren);
+    PERL_UNUSED_ARG(value);
+
+    if (!PL_localizing)
+        Perl_croak_no_modify();
+}
+
+I32
+Perl_reg_numbered_buff_length(pTHX_ REGEXP * const r, const SV * const sv,
+                              const I32 paren)
+{
+    struct regexp *const rx = ReANY(r);
+    I32 i;
+    I32 s1, t1;
+
+    PERL_ARGS_ASSERT_REG_NUMBERED_BUFF_LENGTH;
+
+    if (   paren == RX_BUFF_IDX_CARET_PREMATCH
+        || paren == RX_BUFF_IDX_CARET_FULLMATCH
+        || paren == RX_BUFF_IDX_CARET_POSTMATCH
+    )
+    {
+        bool keepcopy = cBOOL(rx->extflags & RXf_PMf_KEEPCOPY);
+        if (!keepcopy) {
+            /* on something like
+             *    $r = qr/.../;
+             *    /$qr/p;
+             * the KEEPCOPY is set on the PMOP rather than the regex */
+            if (PL_curpm && r == PM_GETRE(PL_curpm))
+                 keepcopy = cBOOL(PL_curpm->op_pmflags & PMf_KEEPCOPY);
+        }
+        if (!keepcopy)
+            goto warn_undef;
+    }
+
+    /* Some of this code was originally in C<Perl_magic_len> in F<mg.c> */
+    switch (paren) {
+      case RX_BUFF_IDX_CARET_PREMATCH: /* ${^PREMATCH} */
+      case RX_BUFF_IDX_PREMATCH:       /* $` */
+        if (rx->offs[0].start != -1) {
+                       i = rx->offs[0].start;
+                       if (i > 0) {
+                               s1 = 0;
+                               t1 = i;
+                               goto getlen;
+                       }
+           }
+        return 0;
+
+      case RX_BUFF_IDX_CARET_POSTMATCH: /* ${^POSTMATCH} */
+      case RX_BUFF_IDX_POSTMATCH:       /* $' */
+           if (rx->offs[0].end != -1) {
+                       i = rx->sublen - rx->offs[0].end;
+                       if (i > 0) {
+                               s1 = rx->offs[0].end;
+                               t1 = rx->sublen;
+                               goto getlen;
+                       }
+           }
+        return 0;
+
+      default: /* $& / ${^MATCH}, $1, $2, ... */
+           if (paren <= (I32)rx->nparens &&
+            (s1 = rx->offs[paren].start) != -1 &&
+            (t1 = rx->offs[paren].end) != -1)
+           {
+            i = t1 - s1;
+            goto getlen;
+        } else {
+          warn_undef:
+            if (ckWARN(WARN_UNINITIALIZED))
+                report_uninit((const SV *)sv);
+            return 0;
+        }
+    }
+  getlen:
+    if (i > 0 && RXp_MATCH_UTF8(rx)) {
+        const char * const s = rx->subbeg - rx->suboffset + s1;
+        const U8 *ep;
+        STRLEN el;
+
+        i = t1 - s1;
+        if (is_utf8_string_loclen((U8*)s, i, &ep, &el))
+                       i = el;
+    }
+    return i;
+}
+
+SV*
+Perl_reg_qr_package(pTHX_ REGEXP * const rx)
+{
+    PERL_ARGS_ASSERT_REG_QR_PACKAGE;
+       PERL_UNUSED_ARG(rx);
+       if (0)
+           return NULL;
+       else
+           return newSVpvs("Regexp");
+}
+
+/* Scans the name of a named buffer from the pattern.
+ * If flags is REG_RSN_RETURN_NULL returns null.
+ * If flags is REG_RSN_RETURN_NAME returns an SV* containing the name
+ * If flags is REG_RSN_RETURN_DATA returns the data SV* corresponding
+ * to the parsed name as looked up in the RExC_paren_names hash.
+ * If there is an error throws a vFAIL().. type exception.
+ */
+
+#define REG_RSN_RETURN_NULL    0
+#define REG_RSN_RETURN_NAME    1
+#define REG_RSN_RETURN_DATA    2
+
+STATIC SV*
+S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
+{
+    char *name_start = RExC_parse;
+
+    PERL_ARGS_ASSERT_REG_SCAN_NAME;
+
+    assert (RExC_parse <= RExC_end);
+    if (RExC_parse == RExC_end) NOOP;
+    else if (isIDFIRST_lazy_if(RExC_parse, UTF)) {
+        /* skip IDFIRST by using do...while */
+       if (UTF)
+           do {
+               RExC_parse += UTF8SKIP(RExC_parse);
+           } while (isWORDCHAR_utf8((U8*)RExC_parse));
+       else
+           do {
+               RExC_parse++;
+           } while (isWORDCHAR(*RExC_parse));
+    } else {
+        RExC_parse++; /* so the <- from the vFAIL is after the offending
+                         character */
+        vFAIL("Group name must start with a non-digit word character");
+    }
+    if ( flags ) {
+        SV* sv_name
+           = newSVpvn_flags(name_start, (int)(RExC_parse - name_start),
+                            SVs_TEMP | (UTF ? SVf_UTF8 : 0));
+        if ( flags == REG_RSN_RETURN_NAME)
+            return sv_name;
+        else if (flags==REG_RSN_RETURN_DATA) {
+            HE *he_str = NULL;
+            SV *sv_dat = NULL;
+            if ( ! sv_name )      /* should not happen*/
+                Perl_croak(aTHX_ "panic: no svname in reg_scan_name");
+            if (RExC_paren_names)
+                he_str = hv_fetch_ent( RExC_paren_names, sv_name, 0, 0 );
+            if ( he_str )
+                sv_dat = HeVAL(he_str);
+            if ( ! sv_dat )
+                vFAIL("Reference to nonexistent named group");
+            return sv_dat;
+        }
+        else {
+            Perl_croak(aTHX_ "panic: bad flag %lx in reg_scan_name",
+                      (unsigned long) flags);
+        }
+        assert(0); /* NOT REACHED */
+    }
+    return NULL;
+}
+
+#define DEBUG_PARSE_MSG(funcname)     DEBUG_PARSE_r({           \
+    int rem=(int)(RExC_end - RExC_parse);                       \
+    int cut;                                                    \
+    int num;                                                    \
+    int iscut=0;                                                \
+    if (rem>10) {                                               \
+        rem=10;                                                 \
+        iscut=1;                                                \
+    }                                                           \
+    cut=10-rem;                                                 \
+    if (RExC_lastparse!=RExC_parse)                             \
+        PerlIO_printf(Perl_debug_log," >%.*s%-*s",              \
+            rem, RExC_parse,                                    \
+            cut + 4,                                            \
+            iscut ? "..." : "<"                                 \
+        );                                                      \
+    else                                                        \
+        PerlIO_printf(Perl_debug_log,"%16s","");                \
+                                                                \
+    if (SIZE_ONLY)                                              \
+       num = RExC_size + 1;                                     \
+    else                                                        \
+       num=REG_NODE_NUM(RExC_emit);                             \
+    if (RExC_lastnum!=num)                                      \
+       PerlIO_printf(Perl_debug_log,"|%4d",num);                \
+    else                                                        \
+       PerlIO_printf(Perl_debug_log,"|%4s","");                 \
+    PerlIO_printf(Perl_debug_log,"|%*s%-4s",                    \
+        (int)((depth*2)), "",                                   \
+        (funcname)                                              \
+    );                                                          \
+    RExC_lastnum=num;                                           \
+    RExC_lastparse=RExC_parse;                                  \
+})
+
+
+
+#define DEBUG_PARSE(funcname)     DEBUG_PARSE_r({           \
+    DEBUG_PARSE_MSG((funcname));                            \
+    PerlIO_printf(Perl_debug_log,"%4s","\n");               \
+})
+#define DEBUG_PARSE_FMT(funcname,fmt,args)     DEBUG_PARSE_r({           \
+    DEBUG_PARSE_MSG((funcname));                            \
+    PerlIO_printf(Perl_debug_log,fmt "\n",args);               \
+})
+
+/* This section of code defines the inversion list object and its methods.  The
+ * interfaces are highly subject to change, so as much as possible is static to
+ * this file.  An inversion list is here implemented as a malloc'd C UV array
+ * as an SVt_INVLIST scalar.
+ *
+ * An inversion list for Unicode is an array of code points, sorted by ordinal
+ * number.  The zeroth element is the first code point in the list.  The 1th
+ * element is the first element beyond that not in the list.  In other words,
+ * the first range is
+ *  invlist[0]..(invlist[1]-1)
+ * The other ranges follow.  Thus every element whose index is divisible by two
+ * marks the beginning of a range that is in the list, and every element not
+ * divisible by two marks the beginning of a range not in the list.  A single
+ * element inversion list that contains the single code point N generally
+ * consists of two elements
+ *  invlist[0] == N
+ *  invlist[1] == N+1
+ * (The exception is when N is the highest representable value on the
+ * machine, in which case the list containing just it would be a single
+ * element, itself.  By extension, if the last range in the list extends to
+ * infinity, then the first element of that range will be in the inversion list
+ * at a position that is divisible by two, and is the final element in the
+ * list.)
+ * Taking the complement (inverting) an inversion list is quite simple, if the
+ * first element is 0, remove it; otherwise add a 0 element at the beginning.
+ * This implementation reserves an element at the beginning of each inversion
+ * list to always contain 0; there is an additional flag in the header which
+ * indicates if the list begins at the 0, or is offset to begin at the next
+ * element.
+ *
+ * More about inversion lists can be found in "Unicode Demystified"
+ * Chapter 13 by Richard Gillam, published by Addison-Wesley.
+ * More will be coming when functionality is added later.
+ *
+ * The inversion list data structure is currently implemented as an SV pointing
+ * to an array of UVs that the SV thinks are bytes.  This allows us to have an
+ * array of UV whose memory management is automatically handled by the existing
+ * facilities for SV's.
+ *
+ * Some of the methods should always be private to the implementation, and some
+ * should eventually be made public */
+
+/* The header definitions are in F<inline_invlist.c> */
+
+PERL_STATIC_INLINE UV*
+S__invlist_array_init(pTHX_ SV* const invlist, const bool will_have_0)
+{
+    /* Returns a pointer to the first element in the inversion list's array.
+     * This is called upon initialization of an inversion list.  Where the
+     * array begins depends on whether the list has the code point U+0000 in it
+     * or not.  The other parameter tells it whether the code that follows this
+     * call is about to put a 0 in the inversion list or not.  The first
+     * element is either the element reserved for 0, if TRUE, or the element
+     * after it, if FALSE */
+
+    bool* offset = get_invlist_offset_addr(invlist);
+    UV* zero_addr = (UV *) SvPVX(invlist);
+
+    PERL_ARGS_ASSERT__INVLIST_ARRAY_INIT;
+
+    /* Must be empty */
+    assert(! _invlist_len(invlist));
+
+    *zero_addr = 0;
+
+    /* 1^1 = 0; 1^0 = 1 */
+    *offset = 1 ^ will_have_0;
+    return zero_addr + *offset;
+}
+
+PERL_STATIC_INLINE UV*
+S_invlist_array(pTHX_ SV* const invlist)
+{
+    /* Returns the pointer to the inversion list's array.  Every time the
+     * length changes, this needs to be called in case malloc or realloc moved
+     * it */
+
+    PERL_ARGS_ASSERT_INVLIST_ARRAY;
+
+    /* Must not be empty.  If these fail, you probably didn't check for <len>
+     * being non-zero before trying to get the array */
+    assert(_invlist_len(invlist));
+
+    /* The very first element always contains zero, The array begins either
+     * there, or if the inversion list is offset, at the element after it.
+     * The offset header field determines which; it contains 0 or 1 to indicate
+     * how much additionally to add */
+    assert(0 == *(SvPVX(invlist)));
+    return ((UV *) SvPVX(invlist) + *get_invlist_offset_addr(invlist));
+}
+
+PERL_STATIC_INLINE void
+S_invlist_set_len(pTHX_ SV* const invlist, const UV len, const bool offset)
+{
+    /* Sets the current number of elements stored in the inversion list.
+     * Updates SvCUR correspondingly */
+
+    PERL_ARGS_ASSERT_INVLIST_SET_LEN;
+
+    assert(SvTYPE(invlist) == SVt_INVLIST);
+
+    SvCUR_set(invlist,
+              (len == 0)
+               ? 0
+               : TO_INTERNAL_SIZE(len + offset));
+    assert(SvLEN(invlist) == 0 || SvCUR(invlist) <= SvLEN(invlist));
+}
+
+PERL_STATIC_INLINE IV*
+S_get_invlist_previous_index_addr(pTHX_ SV* invlist)
+{
+    /* Return the address of the IV that is reserved to hold the cached index
+     * */
+
+    PERL_ARGS_ASSERT_GET_INVLIST_PREVIOUS_INDEX_ADDR;
+
+    assert(SvTYPE(invlist) == SVt_INVLIST);
+
+    return &(((XINVLIST*) SvANY(invlist))->prev_index);
+}
+
+PERL_STATIC_INLINE IV
+S_invlist_previous_index(pTHX_ SV* const invlist)
+{
+    /* Returns cached index of previous search */
+
+    PERL_ARGS_ASSERT_INVLIST_PREVIOUS_INDEX;
+
+    return *get_invlist_previous_index_addr(invlist);
+}
+
+PERL_STATIC_INLINE void
+S_invlist_set_previous_index(pTHX_ SV* const invlist, const IV index)
+{
+    /* Caches <index> for later retrieval */
+
+    PERL_ARGS_ASSERT_INVLIST_SET_PREVIOUS_INDEX;
+
+    assert(index == 0 || index < (int) _invlist_len(invlist));
+
+    *get_invlist_previous_index_addr(invlist) = index;
+}
+
+PERL_STATIC_INLINE UV
+S_invlist_max(pTHX_ SV* const invlist)
+{
+    /* Returns the maximum number of elements storable in the inversion list's
+     * array, without having to realloc() */
+
+    PERL_ARGS_ASSERT_INVLIST_MAX;
+
+    assert(SvTYPE(invlist) == SVt_INVLIST);
+
+    /* Assumes worst case, in which the 0 element is not counted in the
+     * inversion list, so subtracts 1 for that */
+    return SvLEN(invlist) == 0  /* This happens under _new_invlist_C_array */
+           ? FROM_INTERNAL_SIZE(SvCUR(invlist)) - 1
+           : FROM_INTERNAL_SIZE(SvLEN(invlist)) - 1;
+}
+
+#ifndef PERL_IN_XSUB_RE
+SV*
+Perl__new_invlist(pTHX_ IV initial_size)
+{
+
+    /* Return a pointer to a newly constructed inversion list, with enough
+     * space to store 'initial_size' elements.  If that number is negative, a
+     * system default is used instead */
+
+    SV* new_list;
+
+    if (initial_size < 0) {
+       initial_size = 10;
+    }
+
+    /* Allocate the initial space */
+    new_list = newSV_type(SVt_INVLIST);
+
+    /* First 1 is in case the zero element isn't in the list; second 1 is for
+     * trailing NUL */
+    SvGROW(new_list, TO_INTERNAL_SIZE(initial_size + 1) + 1);
+    invlist_set_len(new_list, 0, 0);
+
+    /* Force iterinit() to be used to get iteration to work */
+    *get_invlist_iter_addr(new_list) = (STRLEN) UV_MAX;
+
+    *get_invlist_previous_index_addr(new_list) = 0;
+
+    return new_list;
+}
+
+SV*
+Perl__new_invlist_C_array(pTHX_ const UV* const list)
+{
+    /* Return a pointer to a newly constructed inversion list, initialized to
+     * point to <list>, which has to be in the exact correct inversion list
+     * form, including internal fields.  Thus this is a dangerous routine that
+     * should not be used in the wrong hands.  The passed in 'list' contains
+     * several header fields at the beginning that are not part of the
+     * inversion list body proper */
+
+    const STRLEN length = (STRLEN) list[0];
+    const UV version_id =          list[1];
+    const bool offset   =    cBOOL(list[2]);
+#define HEADER_LENGTH 3
+    /* If any of the above changes in any way, you must change HEADER_LENGTH
+     * (if appropriate) and regenerate INVLIST_VERSION_ID by running
+     *      perl -E 'say int(rand 2**31-1)'
+     */
+#define INVLIST_VERSION_ID 148565664 /* This is a combination of a version and
+                                        data structure type, so that one being
+                                        passed in can be validated to be an
+                                        inversion list of the correct vintage.
+                                       */
+
+    SV* invlist = newSV_type(SVt_INVLIST);
+
+    PERL_ARGS_ASSERT__NEW_INVLIST_C_ARRAY;
+
+    if (version_id != INVLIST_VERSION_ID) {
+        Perl_croak(aTHX_ "panic: Incorrect version for previously generated inversion list");
+    }
+
+    /* The generated array passed in includes header elements that aren't part
+     * of the list proper, so start it just after them */
+    SvPV_set(invlist, (char *) (list + HEADER_LENGTH));
+
+    SvLEN_set(invlist, 0);  /* Means we own the contents, and the system
+                              shouldn't touch it */
+
+    *(get_invlist_offset_addr(invlist)) = offset;
+
+    /* The 'length' passed to us is the physical number of elements in the
+     * inversion list.  But if there is an offset the logical number is one
+     * less than that */
+    invlist_set_len(invlist, length  - offset, offset);
+
+    invlist_set_previous_index(invlist, 0);
+
+    /* Initialize the iteration pointer. */
+    invlist_iterfinish(invlist);
+
+    SvREADONLY_on(invlist);
+
+    return invlist;
+}
+#endif /* ifndef PERL_IN_XSUB_RE */
+
+STATIC void
+S_invlist_extend(pTHX_ SV* const invlist, const UV new_max)
+{
+    /* Grow the maximum size of an inversion list */
+
+    PERL_ARGS_ASSERT_INVLIST_EXTEND;
+
+    assert(SvTYPE(invlist) == SVt_INVLIST);
+
+    /* Add one to account for the zero element at the beginning which may not
+     * be counted by the calling parameters */
+    SvGROW((SV *)invlist, TO_INTERNAL_SIZE(new_max + 1));
+}
+
+PERL_STATIC_INLINE void
+S_invlist_trim(pTHX_ SV* const invlist)
+{
+    PERL_ARGS_ASSERT_INVLIST_TRIM;
+
+    assert(SvTYPE(invlist) == SVt_INVLIST);
+
+    /* Change the length of the inversion list to how many entries it currently
+     * has */
+    SvPV_shrink_to_cur((SV *) invlist);
+}
+
+STATIC void
+S__append_range_to_invlist(pTHX_ SV* const invlist,
+                                 const UV start, const UV end)
+{
+   /* Subject to change or removal.  Append the range from 'start' to 'end' at
+    * the end of the inversion list.  The range must be above any existing
+    * ones. */
+
+    UV* array;
+    UV max = invlist_max(invlist);
+    UV len = _invlist_len(invlist);
+    bool offset;
+
+    PERL_ARGS_ASSERT__APPEND_RANGE_TO_INVLIST;
+
+    if (len == 0) { /* Empty lists must be initialized */
+        offset = start != 0;
+        array = _invlist_array_init(invlist, ! offset);
+    }
+    else {
+       /* Here, the existing list is non-empty. The current max entry in the
+        * list is generally the first value not in the set, except when the
+        * set extends to the end of permissible values, in which case it is
+        * the first entry in that final set, and so this call is an attempt to
+        * append out-of-order */
+
+       UV final_element = len - 1;
+       array = invlist_array(invlist);
+       if (array[final_element] > start
+           || ELEMENT_RANGE_MATCHES_INVLIST(final_element))
+       {
+           Perl_croak(aTHX_ "panic: attempting to append to an inversion list, but wasn't at the end of the list, final=%"UVuf", start=%"UVuf", match=%c",
+                    array[final_element], start,
+                    ELEMENT_RANGE_MATCHES_INVLIST(final_element) ? 't' : 'f');
+       }
+
+       /* Here, it is a legal append.  If the new range begins with the first
+        * value not in the set, it is extending the set, so the new first
+        * value not in the set is one greater than the newly extended range.
+        * */
+        offset = *get_invlist_offset_addr(invlist);
+       if (array[final_element] == start) {
+           if (end != UV_MAX) {
+               array[final_element] = end + 1;
+           }
+           else {
+               /* But if the end is the maximum representable on the machine,
+                * just let the range that this would extend to have no end */
+               invlist_set_len(invlist, len - 1, offset);
+           }
+           return;
+       }
+    }
+
+    /* Here the new range doesn't extend any existing set.  Add it */
+
+    len += 2;  /* Includes an element each for the start and end of range */
+
+    /* If wll overflow the existing space, extend, which may cause the array to
+     * be moved */
+    if (max < len) {
+       invlist_extend(invlist, len);
+
+        /* Have to set len here to avoid assert failure in invlist_array() */
+        invlist_set_len(invlist, len, offset);
+
+       array = invlist_array(invlist);
+    }
+    else {
+       invlist_set_len(invlist, len, offset);
+    }
+
+    /* The next item on the list starts the range, the one after that is
+     * one past the new range.  */
+    array[len - 2] = start;
+    if (end != UV_MAX) {
+       array[len - 1] = end + 1;
+    }
+    else {
+       /* But if the end is the maximum representable on the machine, just let
+        * the range have no end */
+       invlist_set_len(invlist, len - 1, offset);
+    }
+}
+
+#ifndef PERL_IN_XSUB_RE
+
+IV
+Perl__invlist_search(pTHX_ SV* const invlist, const UV cp)
+{
+    /* Searches the inversion list for the entry that contains the input code
+     * point <cp>.  If <cp> is not in the list, -1 is returned.  Otherwise, the
+     * return value is the index into the list's array of the range that
+     * contains <cp> */
+
+    IV low = 0;
+    IV mid;
+    IV high = _invlist_len(invlist);
+    const IV highest_element = high - 1;
+    const UV* array;
+
+    PERL_ARGS_ASSERT__INVLIST_SEARCH;
+
+    /* If list is empty, return failure. */
+    if (high == 0) {
+       return -1;
+    }
+
+    /* (We can't get the array unless we know the list is non-empty) */
+    array = invlist_array(invlist);
+
+    mid = invlist_previous_index(invlist);
+    assert(mid >=0 && mid <= highest_element);
+
+    /* <mid> contains the cache of the result of the previous call to this
+     * function (0 the first time).  See if this call is for the same result,
+     * or if it is for mid-1.  This is under the theory that calls to this
+     * function will often be for related code points that are near each other.
+     * And benchmarks show that caching gives better results.  We also test
+     * here if the code point is within the bounds of the list.  These tests
+     * replace others that would have had to be made anyway to make sure that
+     * the array bounds were not exceeded, and these give us extra information
+     * at the same time */
+    if (cp >= array[mid]) {
+        if (cp >= array[highest_element]) {
+            return highest_element;
+        }
+
+        /* Here, array[mid] <= cp < array[highest_element].  This means that
+         * the final element is not the answer, so can exclude it; it also
+         * means that <mid> is not the final element, so can refer to 'mid + 1'
+         * safely */
+        if (cp < array[mid + 1]) {
+            return mid;
+        }
+        high--;
+        low = mid + 1;
+    }
+    else { /* cp < aray[mid] */
+        if (cp < array[0]) { /* Fail if outside the array */
+            return -1;
+        }
+        high = mid;
+        if (cp >= array[mid - 1]) {
+            goto found_entry;
+        }
+    }
+
+    /* Binary search.  What we are looking for is <i> such that
+     * array[i] <= cp < array[i+1]
+     * The loop below converges on the i+1.  Note that there may not be an
+     * (i+1)th element in the array, and things work nonetheless */
+    while (low < high) {
+       mid = (low + high) / 2;
+        assert(mid <= highest_element);
+       if (array[mid] <= cp) { /* cp >= array[mid] */
+           low = mid + 1;
+
+           /* We could do this extra test to exit the loop early.
+           if (cp < array[low]) {
+               return mid;
+           }
+           */
+       }
+       else { /* cp < array[mid] */
+           high = mid;
+       }
+    }
+
+  found_entry:
+    high--;
+    invlist_set_previous_index(invlist, high);
+    return high;
+}
+
+void
+Perl__invlist_populate_swatch(pTHX_ SV* const invlist,
+                                    const UV start, const UV end, U8* swatch)
+{
+    /* populates a swatch of a swash the same way swatch_get() does in utf8.c,
+     * but is used when the swash has an inversion list.  This makes this much
+     * faster, as it uses a binary search instead of a linear one.  This is
+     * intimately tied to that function, and perhaps should be in utf8.c,
+     * except it is intimately tied to inversion lists as well.  It assumes
+     * that <swatch> is all 0's on input */
+
+    UV current = start;
+    const IV len = _invlist_len(invlist);
+    IV i;
+    const UV * array;
+
+    PERL_ARGS_ASSERT__INVLIST_POPULATE_SWATCH;
+
+    if (len == 0) { /* Empty inversion list */
+        return;
+    }
+
+    array = invlist_array(invlist);
+
+    /* Find which element it is */
+    i = _invlist_search(invlist, start);
+
+    /* We populate from <start> to <end> */
+    while (current < end) {
+        UV upper;
+
+       /* The inversion list gives the results for every possible code point
+        * after the first one in the list.  Only those ranges whose index is
+        * even are ones that the inversion list matches.  For the odd ones,
+        * and if the initial code point is not in the list, we have to skip
+        * forward to the next element */
+        if (i == -1 || ! ELEMENT_RANGE_MATCHES_INVLIST(i)) {
+            i++;
+            if (i >= len) { /* Finished if beyond the end of the array */
+                return;
+            }
+            current = array[i];
+           if (current >= end) {   /* Finished if beyond the end of what we
+                                      are populating */
+                if (LIKELY(end < UV_MAX)) {
+                    return;
+                }
+
+                /* We get here when the upper bound is the maximum
+                 * representable on the machine, and we are looking for just
+                 * that code point.  Have to special case it */
+                i = len;
+                goto join_end_of_list;
+            }
+        }
+        assert(current >= start);
+
+       /* The current range ends one below the next one, except don't go past
+        * <end> */
+        i++;
+        upper = (i < len && array[i] < end) ? array[i] : end;
+
+       /* Here we are in a range that matches.  Populate a bit in the 3-bit U8
+        * for each code point in it */
+        for (; current < upper; current++) {
+            const STRLEN offset = (STRLEN)(current - start);
+            swatch[offset >> 3] |= 1 << (offset & 7);
+        }
+
+    join_end_of_list:
+
+       /* Quit if at the end of the list */
+        if (i >= len) {
+
+           /* But first, have to deal with the highest possible code point on
+            * the platform.  The previous code assumes that <end> is one
+            * beyond where we want to populate, but that is impossible at the
+            * platform's infinity, so have to handle it specially */
+            if (UNLIKELY(end == UV_MAX && ELEMENT_RANGE_MATCHES_INVLIST(len-1)))
+           {
+                const STRLEN offset = (STRLEN)(end - start);
+                swatch[offset >> 3] |= 1 << (offset & 7);
+            }
+            return;
+        }
+
+       /* Advance to the next range, which will be for code points not in the
+        * inversion list */
+        current = array[i];
+    }
+
+    return;
+}
+
+void
+Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
+                                         const bool complement_b, SV** output)
+{
+    /* Take the union of two inversion lists and point <output> to it.  *output
+     * SHOULD BE DEFINED upon input, and if it points to one of the two lists,
+     * the reference count to that list will be decremented if not already a
+     * temporary (mortal); otherwise *output will be made correspondingly
+     * mortal.  The first list, <a>, may be NULL, in which case a copy of the
+     * second list is returned.  If <complement_b> is TRUE, the union is taken
+     * of the complement (inversion) of <b> instead of b itself.
+     *
+     * The basis for this comes from "Unicode Demystified" Chapter 13 by
+     * Richard Gillam, published by Addison-Wesley, and explained at some
+     * length there.  The preface says to incorporate its examples into your
+     * code at your own risk.
+     *
+     * The algorithm is like a merge sort.
+     *
+     * XXX A potential performance improvement is to keep track as we go along
+     * if only one of the inputs contributes to the result, meaning the other
+     * is a subset of that one.  In that case, we can skip the final copy and
+     * return the larger of the input lists, but then outside code might need
+     * to keep track of whether to free the input list or not */
+
+    const UV* array_a;    /* a's array */
+    const UV* array_b;
+    UV len_a;      /* length of a's array */
+    UV len_b;
+
+    SV* u;                     /* the resulting union */
+    UV* array_u;
+    UV len_u;
+
+    UV i_a = 0;                    /* current index into a's array */
+    UV i_b = 0;
+    UV i_u = 0;
+
+    /* running count, as explained in the algorithm source book; items are
+     * stopped accumulating and are output when the count changes to/from 0.
+     * The count is incremented when we start a range that's in the set, and
+     * decremented when we start a range that's not in the set.  So its range
+     * is 0 to 2.  Only when the count is zero is something not in the set.
+     */
+    UV count = 0;
+
+    PERL_ARGS_ASSERT__INVLIST_UNION_MAYBE_COMPLEMENT_2ND;
+    assert(a != b);
+
+    /* If either one is empty, the union is the other one */
+    if (a == NULL || ((len_a = _invlist_len(a)) == 0)) {
+        bool make_temp = FALSE; /* Should we mortalize the result? */
+
+       if (*output == a) {
+            if (a != NULL) {
+                if (! (make_temp = cBOOL(SvTEMP(a)))) {
+                    SvREFCNT_dec_NN(a);
+                }
+            }
+       }
+       if (*output != b) {
+           *output = invlist_clone(b);
+            if (complement_b) {
+                _invlist_invert(*output);
+            }
+       } /* else *output already = b; */
+
+        if (make_temp) {
+            sv_2mortal(*output);
+        }
+       return;
+    }
+    else if ((len_b = _invlist_len(b)) == 0) {
+        bool make_temp = FALSE;
+       if (*output == b) {
+            if (! (make_temp = cBOOL(SvTEMP(b)))) {
+                SvREFCNT_dec_NN(b);
+            }
+       }
+
+        /* The complement of an empty list is a list that has everything in it,
+         * so the union with <a> includes everything too */
+        if (complement_b) {
+            if (a == *output) {
+                if (! (make_temp = cBOOL(SvTEMP(a)))) {
+                    SvREFCNT_dec_NN(a);
+                }
+            }
+            *output = _new_invlist(1);
+            _append_range_to_invlist(*output, 0, UV_MAX);
+        }
+        else if (*output != a) {
+            *output = invlist_clone(a);
+        }
+        /* else *output already = a; */
+
+        if (make_temp) {
+            sv_2mortal(*output);
+        }
+       return;
+    }
+
+    /* Here both lists exist and are non-empty */
+    array_a = invlist_array(a);
+    array_b = invlist_array(b);
+
+    /* If are to take the union of 'a' with the complement of b, set it
+     * up so are looking at b's complement. */
+    if (complement_b) {
+
+       /* To complement, we invert: if the first element is 0, remove it.  To
+        * do this, we just pretend the array starts one later */
+        if (array_b[0] == 0) {
+            array_b++;
+            len_b--;
+        }
+        else {
+
+            /* But if the first element is not zero, we pretend the list starts
+             * at the 0 that is always stored immediately before the array. */
+            array_b--;
+            len_b++;
+        }
+    }
+
+    /* Size the union for the worst case: that the sets are completely
+     * disjoint */
+    u = _new_invlist(len_a + len_b);
+
+    /* Will contain U+0000 if either component does */
+    array_u = _invlist_array_init(u, (len_a > 0 && array_a[0] == 0)
+                                     || (len_b > 0 && array_b[0] == 0));
+
+    /* Go through each list item by item, stopping when exhausted one of
+     * them */
+    while (i_a < len_a && i_b < len_b) {
+       UV cp;      /* The element to potentially add to the union's array */
+       bool cp_in_set;   /* is it in the the input list's set or not */
+
+       /* We need to take one or the other of the two inputs for the union.
+        * Since we are merging two sorted lists, we take the smaller of the
+        * next items.  In case of a tie, we take the one that is in its set
+        * first.  If we took one not in the set first, it would decrement the
+        * count, possibly to 0 which would cause it to be output as ending the
+        * range, and the next time through we would take the same number, and
+        * output it again as beginning the next range.  By doing it the
+        * opposite way, there is no possibility that the count will be
+        * momentarily decremented to 0, and thus the two adjoining ranges will
+        * be seamlessly merged.  (In a tie and both are in the set or both not
+        * in the set, it doesn't matter which we take first.) */
+       if (array_a[i_a] < array_b[i_b]
+           || (array_a[i_a] == array_b[i_b]
+               && ELEMENT_RANGE_MATCHES_INVLIST(i_a)))
+       {
+           cp_in_set = ELEMENT_RANGE_MATCHES_INVLIST(i_a);
+           cp= array_a[i_a++];
+       }
+       else {
+           cp_in_set = ELEMENT_RANGE_MATCHES_INVLIST(i_b);
+           cp = array_b[i_b++];
+       }
+
+       /* Here, have chosen which of the two inputs to look at.  Only output
+        * if the running count changes to/from 0, which marks the
+        * beginning/end of a range in that's in the set */
+       if (cp_in_set) {
+           if (count == 0) {
+               array_u[i_u++] = cp;
+           }
+           count++;
+       }
+       else {
+           count--;
+           if (count == 0) {
+               array_u[i_u++] = cp;
+           }
+       }
+    }
+
+    /* Here, we are finished going through at least one of the lists, which
+     * means there is something remaining in at most one.  We check if the list
+     * that hasn't been exhausted is positioned such that we are in the middle
+     * of a range in its set or not.  (i_a and i_b point to the element beyond
+     * the one we care about.) If in the set, we decrement 'count'; if 0, there
+     * is potentially more to output.
+     * There are four cases:
+     * 1) Both weren't in their sets, count is 0, and remains 0.  What's left
+     *    in the union is entirely from the non-exhausted set.
+     * 2) Both were in their sets, count is 2.  Nothing further should
+     *    be output, as everything that remains will be in the exhausted
+     *    list's set, hence in the union; decrementing to 1 but not 0 insures
+     *    that
+     * 3) the exhausted was in its set, non-exhausted isn't, count is 1.
+     *    Nothing further should be output because the union includes
+     *    everything from the exhausted set.  Not decrementing ensures that.
+     * 4) the exhausted wasn't in its set, non-exhausted is, count is 1;
+     *    decrementing to 0 insures that we look at the remainder of the
+     *    non-exhausted set */
+    if ((i_a != len_a && PREV_RANGE_MATCHES_INVLIST(i_a))
+       || (i_b != len_b && PREV_RANGE_MATCHES_INVLIST(i_b)))
+    {
+       count--;
+    }
+
+    /* The final length is what we've output so far, plus what else is about to
+     * be output.  (If 'count' is non-zero, then the input list we exhausted
+     * has everything remaining up to the machine's limit in its set, and hence
+     * in the union, so there will be no further output. */
+    len_u = i_u;
+    if (count == 0) {
+       /* At most one of the subexpressions will be non-zero */
+       len_u += (len_a - i_a) + (len_b - i_b);
+    }
+
+    /* Set result to final length, which can change the pointer to array_u, so
+     * re-find it */
+    if (len_u != _invlist_len(u)) {
+       invlist_set_len(u, len_u, *get_invlist_offset_addr(u));
+       invlist_trim(u);
+       array_u = invlist_array(u);
+    }
+
+    /* When 'count' is 0, the list that was exhausted (if one was shorter than
+     * the other) ended with everything above it not in its set.  That means
+     * that the remaining part of the union is precisely the same as the
+     * non-exhausted list, so can just copy it unchanged.  (If both list were
+     * exhausted at the same time, then the operations below will be both 0.)
+     */
+    if (count == 0) {
+       IV copy_count; /* At most one will have a non-zero copy count */
+       if ((copy_count = len_a - i_a) > 0) {
+           Copy(array_a + i_a, array_u + i_u, copy_count, UV);
+       }
+       else if ((copy_count = len_b - i_b) > 0) {
+           Copy(array_b + i_b, array_u + i_u, copy_count, UV);
+       }
+    }
+
+    /*  We may be removing a reference to one of the inputs.  If so, the output
+     *  is made mortal if the input was.  (Mortal SVs shouldn't have their ref
+     *  count decremented) */
+    if (a == *output || b == *output) {
+        assert(! invlist_is_iterating(*output));
+        if ((SvTEMP(*output))) {
+            sv_2mortal(u);
+        }
+        else {
+            SvREFCNT_dec_NN(*output);
+        }
+    }
+
+    *output = u;
+
+    return;
+}
+
+void
+Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
+                                               const bool complement_b, SV** i)
+{
+    /* Take the intersection of two inversion lists and point <i> to it.  *i
+     * SHOULD BE DEFINED upon input, and if it points to one of the two lists,
+     * the reference count to that list will be decremented if not already a
+     * temporary (mortal); otherwise *i will be made correspondingly mortal.
+     * The first list, <a>, may be NULL, in which case an empty list is
+     * returned.  If <complement_b> is TRUE, the result will be the
+     * intersection of <a> and the complement (or inversion) of <b> instead of
+     * <b> directly.
+     *
+     * The basis for this comes from "Unicode Demystified" Chapter 13 by
+     * Richard Gillam, published by Addison-Wesley, and explained at some
+     * length there.  The preface says to incorporate its examples into your
+     * code at your own risk.  In fact, it had bugs
+     *
+     * The algorithm is like a merge sort, and is essentially the same as the
+     * union above
+     */
+
+    const UV* array_a;         /* a's array */
+    const UV* array_b;
+    UV len_a;  /* length of a's array */
+    UV len_b;
+
+    SV* r;                  /* the resulting intersection */
+    UV* array_r;
+    UV len_r;
+
+    UV i_a = 0;                    /* current index into a's array */
+    UV i_b = 0;
+    UV i_r = 0;
+
+    /* running count, as explained in the algorithm source book; items are
+     * stopped accumulating and are output when the count changes to/from 2.
+     * The count is incremented when we start a range that's in the set, and
+     * decremented when we start a range that's not in the set.  So its range
+     * is 0 to 2.  Only when the count is 2 is something in the intersection.
+     */
+    UV count = 0;
+
+    PERL_ARGS_ASSERT__INVLIST_INTERSECTION_MAYBE_COMPLEMENT_2ND;
+    assert(a != b);
+
+    /* Special case if either one is empty */
+    len_a = (a == NULL) ? 0 : _invlist_len(a);
+    if ((len_a == 0) || ((len_b = _invlist_len(b)) == 0)) {
+        bool make_temp = FALSE;
+
+        if (len_a != 0 && complement_b) {
+
+            /* Here, 'a' is not empty, therefore from the above 'if', 'b' must
+             * be empty.  Here, also we are using 'b's complement, which hence
+             * must be every possible code point.  Thus the intersection is
+             * simply 'a'. */
+            if (*i != a) {
+                if (*i == b) {
+                    if (! (make_temp = cBOOL(SvTEMP(b)))) {
+                        SvREFCNT_dec_NN(b);
+                    }
+                }
+
+                *i = invlist_clone(a);
+            }
+            /* else *i is already 'a' */
+
+            if (make_temp) {
+                sv_2mortal(*i);
+            }
+            return;
+        }
+
+        /* Here, 'a' or 'b' is empty and not using the complement of 'b'.  The
+         * intersection must be empty */
+       if (*i == a) {
+            if (! (make_temp = cBOOL(SvTEMP(a)))) {
+                SvREFCNT_dec_NN(a);
+            }
+       }
+       else if (*i == b) {
+            if (! (make_temp = cBOOL(SvTEMP(b)))) {
+                SvREFCNT_dec_NN(b);
+            }
+       }
+       *i = _new_invlist(0);
+        if (make_temp) {
+            sv_2mortal(*i);
+        }
+
+       return;
+    }
+
+    /* Here both lists exist and are non-empty */
+    array_a = invlist_array(a);
+    array_b = invlist_array(b);
+
+    /* If are to take the intersection of 'a' with the complement of b, set it
+     * up so are looking at b's complement. */
+    if (complement_b) {
+
+       /* To complement, we invert: if the first element is 0, remove it.  To
+        * do this, we just pretend the array starts one later */
+        if (array_b[0] == 0) {
+            array_b++;
+            len_b--;
+        }
+        else {
+
+            /* But if the first element is not zero, we pretend the list starts
+             * at the 0 that is always stored immediately before the array. */
+            array_b--;
+            len_b++;
+        }
+    }
+
+    /* Size the intersection for the worst case: that the intersection ends up
+     * fragmenting everything to be completely disjoint */
+    r= _new_invlist(len_a + len_b);
+
+    /* Will contain U+0000 iff both components do */
+    array_r = _invlist_array_init(r, len_a > 0 && array_a[0] == 0
+                                    && len_b > 0 && array_b[0] == 0);
+
+    /* Go through each list item by item, stopping when exhausted one of
+     * them */
+    while (i_a < len_a && i_b < len_b) {
+       UV cp;      /* The element to potentially add to the intersection's
+                      array */
+       bool cp_in_set; /* Is it in the input list's set or not */
+
+       /* We need to take one or the other of the two inputs for the
+        * intersection.  Since we are merging two sorted lists, we take the
+        * smaller of the next items.  In case of a tie, we take the one that
+        * is not in its set first (a difference from the union algorithm).  If
+        * we took one in the set first, it would increment the count, possibly
+        * to 2 which would cause it to be output as starting a range in the
+        * intersection, and the next time through we would take that same
+        * number, and output it again as ending the set.  By doing it the
+        * opposite of this, there is no possibility that the count will be
+        * momentarily incremented to 2.  (In a tie and both are in the set or
+        * both not in the set, it doesn't matter which we take first.) */
+       if (array_a[i_a] < array_b[i_b]
+           || (array_a[i_a] == array_b[i_b]
+               && ! ELEMENT_RANGE_MATCHES_INVLIST(i_a)))
+       {
+           cp_in_set = ELEMENT_RANGE_MATCHES_INVLIST(i_a);
+           cp= array_a[i_a++];
+       }
+       else {
+           cp_in_set = ELEMENT_RANGE_MATCHES_INVLIST(i_b);
+           cp= array_b[i_b++];
+       }
+
+       /* Here, have chosen which of the two inputs to look at.  Only output
+        * if the running count changes to/from 2, which marks the
+        * beginning/end of a range that's in the intersection */
+       if (cp_in_set) {
+           count++;
+           if (count == 2) {
+               array_r[i_r++] = cp;
+           }
+       }
+       else {
+           if (count == 2) {
+               array_r[i_r++] = cp;
+           }
+           count--;
+       }
+    }
+
+    /* Here, we are finished going through at least one of the lists, which
+     * means there is something remaining in at most one.  We check if the list
+     * that has been exhausted is positioned such that we are in the middle
+     * of a range in its set or not.  (i_a and i_b point to elements 1 beyond
+     * the ones we care about.)  There are four cases:
+     * 1) Both weren't in their sets, count is 0, and remains 0.  There's
+     *    nothing left in the intersection.
+     * 2) Both were in their sets, count is 2 and perhaps is incremented to
+     *    above 2.  What should be output is exactly that which is in the
+     *    non-exhausted set, as everything it has is also in the intersection
+     *    set, and everything it doesn't have can't be in the intersection
+     * 3) The exhausted was in its set, non-exhausted isn't, count is 1, and
+     *    gets incremented to 2.  Like the previous case, the intersection is
+     *    everything that remains in the non-exhausted set.
+     * 4) the exhausted wasn't in its set, non-exhausted is, count is 1, and
+     *    remains 1.  And the intersection has nothing more. */
+    if ((i_a == len_a && PREV_RANGE_MATCHES_INVLIST(i_a))
+       || (i_b == len_b && PREV_RANGE_MATCHES_INVLIST(i_b)))
+    {
+       count++;
+    }
+
+    /* The final length is what we've output so far plus what else is in the
+     * intersection.  At most one of the subexpressions below will be non-zero
+     * */
+    len_r = i_r;
+    if (count >= 2) {
+       len_r += (len_a - i_a) + (len_b - i_b);
+    }
+
+    /* Set result to final length, which can change the pointer to array_r, so
+     * re-find it */
+    if (len_r != _invlist_len(r)) {
+       invlist_set_len(r, len_r, *get_invlist_offset_addr(r));
+       invlist_trim(r);
+       array_r = invlist_array(r);
+    }
+
+    /* Finish outputting any remaining */
+    if (count >= 2) { /* At most one will have a non-zero copy count */
+       IV copy_count;
+       if ((copy_count = len_a - i_a) > 0) {
+           Copy(array_a + i_a, array_r + i_r, copy_count, UV);
+       }
+       else if ((copy_count = len_b - i_b) > 0) {
+           Copy(array_b + i_b, array_r + i_r, copy_count, UV);
+       }
+    }
+
+    /*  We may be removing a reference to one of the inputs.  If so, the output
+     *  is made mortal if the input was.  (Mortal SVs shouldn't have their ref
+     *  count decremented) */
+    if (a == *i || b == *i) {
+        assert(! invlist_is_iterating(*i));
+        if (SvTEMP(*i)) {
+            sv_2mortal(r);
+        }
+        else {
+            SvREFCNT_dec_NN(*i);
+        }
+    }
+
+    *i = r;
+
+    return;
+}
+
+SV*
+Perl__add_range_to_invlist(pTHX_ SV* invlist, const UV start, const UV end)
+{
+    /* Add the range from 'start' to 'end' inclusive to the inversion list's
+     * set.  A pointer to the inversion list is returned.  This may actually be
+     * a new list, in which case the passed in one has been destroyed.  The
+     * passed in inversion list can be NULL, in which case a new one is created
+     * with just the one range in it */
+
+    SV* range_invlist;
+    UV len;
+
+    if (invlist == NULL) {
+       invlist = _new_invlist(2);
+       len = 0;
+    }
+    else {
+       len = _invlist_len(invlist);
+    }
+
+    /* If comes after the final entry actually in the list, can just append it
+     * to the end, */
+    if (len == 0
+       || (! ELEMENT_RANGE_MATCHES_INVLIST(len - 1)
+            && start >= invlist_array(invlist)[len - 1]))
+    {
+       _append_range_to_invlist(invlist, start, end);
+       return invlist;
+    }
+
+    /* Here, can't just append things, create and return a new inversion list
+     * which is the union of this range and the existing inversion list */
+    range_invlist = _new_invlist(2);
+    _append_range_to_invlist(range_invlist, start, end);
+
+    _invlist_union(invlist, range_invlist, &invlist);
+
+    /* The temporary can be freed */
+    SvREFCNT_dec_NN(range_invlist);
+
+    return invlist;
+}
+
+SV*
+Perl__setup_canned_invlist(pTHX_ const STRLEN size, const UV element0,
+                                 UV** other_elements_ptr)
+{
+    /* Create and return an inversion list whose contents are to be populated
+     * by the caller.  The caller gives the number of elements (in 'size') and
+     * the very first element ('element0').  This function will set
+     * '*other_elements_ptr' to an array of UVs, where the remaining elements
+     * are to be placed.
+     *
+     * Obviously there is some trust involved that the caller will properly
+     * fill in the other elements of the array.
+     *
+     * (The first element needs to be passed in, as the underlying code does
+     * things differently depending on whether it is zero or non-zero) */
+
+    SV* invlist = _new_invlist(size);
+    bool offset;
+
+    PERL_ARGS_ASSERT__SETUP_CANNED_INVLIST;
+
+    _append_range_to_invlist(invlist, element0, element0);
+    offset = *get_invlist_offset_addr(invlist);
+
+    invlist_set_len(invlist, size, offset);
+    *other_elements_ptr = invlist_array(invlist) + 1;
+    return invlist;
+}
+
+#endif
+
+PERL_STATIC_INLINE SV*
+S_add_cp_to_invlist(pTHX_ SV* invlist, const UV cp) {
+    return _add_range_to_invlist(invlist, cp, cp);
+}
+
+#ifndef PERL_IN_XSUB_RE
+void
+Perl__invlist_invert(pTHX_ SV* const invlist)
+{
+    /* Complement the input inversion list.  This adds a 0 if the list didn't
+     * have a zero; removes it otherwise.  As described above, the data
+     * structure is set up so that this is very efficient */
+
+    PERL_ARGS_ASSERT__INVLIST_INVERT;
+
+    assert(! invlist_is_iterating(invlist));
+
+    /* The inverse of matching nothing is matching everything */
+    if (_invlist_len(invlist) == 0) {
+       _append_range_to_invlist(invlist, 0, UV_MAX);
+       return;
+    }
+
+    *get_invlist_offset_addr(invlist) = ! *get_invlist_offset_addr(invlist);
+}
+
+#endif
+
+PERL_STATIC_INLINE SV*
+S_invlist_clone(pTHX_ SV* const invlist)
+{
+
+    /* Return a new inversion list that is a copy of the input one, which is
+     * unchanged.  The new list will not be mortal even if the old one was. */
+
+    /* Need to allocate extra space to accommodate Perl's addition of a
+     * trailing NUL to SvPV's, since it thinks they are always strings */
+    SV* new_invlist = _new_invlist(_invlist_len(invlist) + 1);
+    STRLEN physical_length = SvCUR(invlist);
+    bool offset = *(get_invlist_offset_addr(invlist));
+
+    PERL_ARGS_ASSERT_INVLIST_CLONE;
+
+    *(get_invlist_offset_addr(new_invlist)) = offset;
+    invlist_set_len(new_invlist, _invlist_len(invlist), offset);
+    Copy(SvPVX(invlist), SvPVX(new_invlist), physical_length, char);
+
+    return new_invlist;
+}
+
+PERL_STATIC_INLINE STRLEN*
+S_get_invlist_iter_addr(pTHX_ SV* invlist)
+{
+    /* Return the address of the UV that contains the current iteration
+     * position */
+
+    PERL_ARGS_ASSERT_GET_INVLIST_ITER_ADDR;
+
+    assert(SvTYPE(invlist) == SVt_INVLIST);
+
+    return &(((XINVLIST*) SvANY(invlist))->iterator);
+}
+
+PERL_STATIC_INLINE void
+S_invlist_iterinit(pTHX_ SV* invlist)  /* Initialize iterator for invlist */
+{
+    PERL_ARGS_ASSERT_INVLIST_ITERINIT;
+
+    *get_invlist_iter_addr(invlist) = 0;
+}
+
+PERL_STATIC_INLINE void
+S_invlist_iterfinish(pTHX_ SV* invlist)
+{
+    /* Terminate iterator for invlist.  This is to catch development errors.
+     * Any iteration that is interrupted before completed should call this
+     * function.  Functions that add code points anywhere else but to the end
+     * of an inversion list assert that they are not in the middle of an
+     * iteration.  If they were, the addition would make the iteration
+     * problematical: if the iteration hadn't reached the place where things
+     * were being added, it would be ok */
+
+    PERL_ARGS_ASSERT_INVLIST_ITERFINISH;
+
+    *get_invlist_iter_addr(invlist) = (STRLEN) UV_MAX;
+}
+
+STATIC bool
+S_invlist_iternext(pTHX_ SV* invlist, UV* start, UV* end)
+{
+    /* An C<invlist_iterinit> call on <invlist> must be used to set this up.
+     * This call sets in <*start> and <*end>, the next range in <invlist>.
+     * Returns <TRUE> if successful and the next call will return the next
+     * range; <FALSE> if was already at the end of the list.  If the latter,
+     * <*start> and <*end> are unchanged, and the next call to this function
+     * will start over at the beginning of the list */
+
+    STRLEN* pos = get_invlist_iter_addr(invlist);
+    UV len = _invlist_len(invlist);
+    UV *array;
+
+    PERL_ARGS_ASSERT_INVLIST_ITERNEXT;
+
+    if (*pos >= len) {
+       *pos = (STRLEN) UV_MAX; /* Force iterinit() to be required next time */
+       return FALSE;
+    }
+
+    array = invlist_array(invlist);
+
+    *start = array[(*pos)++];
+
+    if (*pos >= len) {
+       *end = UV_MAX;
+    }
+    else {
+       *end = array[(*pos)++] - 1;
+    }
+
+    return TRUE;
+}
+
+PERL_STATIC_INLINE bool
+S_invlist_is_iterating(pTHX_ SV* const invlist)
+{
+    PERL_ARGS_ASSERT_INVLIST_IS_ITERATING;
+
+    return *(get_invlist_iter_addr(invlist)) < (STRLEN) UV_MAX;
+}
+
+PERL_STATIC_INLINE UV
+S_invlist_highest(pTHX_ SV* const invlist)
+{
+    /* Returns the highest code point that matches an inversion list.  This API
+     * has an ambiguity, as it returns 0 under either the highest is actually
+     * 0, or if the list is empty.  If this distinction matters to you, check
+     * for emptiness before calling this function */
+
+    UV len = _invlist_len(invlist);
+    UV *array;
+
+    PERL_ARGS_ASSERT_INVLIST_HIGHEST;
+
+    if (len == 0) {
+       return 0;
+    }
+
+    array = invlist_array(invlist);
+
+    /* The last element in the array in the inversion list always starts a
+     * range that goes to infinity.  That range may be for code points that are
+     * matched in the inversion list, or it may be for ones that aren't
+     * matched.  In the latter case, the highest code point in the set is one
+     * less than the beginning of this range; otherwise it is the final element
+     * of this range: infinity */
+    return (ELEMENT_RANGE_MATCHES_INVLIST(len - 1))
+           ? UV_MAX
+           : array[len - 1] - 1;
+}
+
+#ifndef PERL_IN_XSUB_RE
+SV *
+Perl__invlist_contents(pTHX_ SV* const invlist)
+{
+    /* Get the contents of an inversion list into a string SV so that they can
+     * be printed out.  It uses the format traditionally done for debug tracing
+     */
+
+    UV start, end;
+    SV* output = newSVpvs("\n");
+
+    PERL_ARGS_ASSERT__INVLIST_CONTENTS;
+
+    assert(! invlist_is_iterating(invlist));
+
+    invlist_iterinit(invlist);
+    while (invlist_iternext(invlist, &start, &end)) {
+       if (end == UV_MAX) {
+           Perl_sv_catpvf(aTHX_ output, "%04"UVXf"\tINFINITY\n", start);
+       }
+       else if (end != start) {
+           Perl_sv_catpvf(aTHX_ output, "%04"UVXf"\t%04"UVXf"\n",
+                   start,       end);
+       }
+       else {
+           Perl_sv_catpvf(aTHX_ output, "%04"UVXf"\n", start);
+       }
+    }
+
+    return output;
+}
+#endif
+
+#ifndef PERL_IN_XSUB_RE
+void
+Perl__invlist_dump(pTHX_ PerlIO *file, I32 level,
+                         const char * const indent, SV* const invlist)
+{
+    /* Designed to be called only by do_sv_dump().  Dumps out the ranges of the
+     * inversion list 'invlist' to 'file' at 'level'  Each line is prefixed by
+     * the string 'indent'.  The output looks like this:
+         [0] 0x000A .. 0x000D
+         [2] 0x0085
+         [4] 0x2028 .. 0x2029
+         [6] 0x3104 .. INFINITY
+     * This means that the first range of code points matched by the list are
+     * 0xA through 0xD; the second range contains only the single code point
+     * 0x85, etc.  An inversion list is an array of UVs.  Two array elements
+     * are used to define each range (except if the final range extends to
+     * infinity, only a single element is needed).  The array index of the
+     * first element for the corresponding range is given in brackets. */
+
+    UV start, end;
+    STRLEN count = 0;
+
+    PERL_ARGS_ASSERT__INVLIST_DUMP;
+
+    if (invlist_is_iterating(invlist)) {
+        Perl_dump_indent(aTHX_ level, file,
+             "%sCan't dump inversion list because is in middle of iterating\n",
+             indent);
+        return;
+    }
+
+    invlist_iterinit(invlist);
+    while (invlist_iternext(invlist, &start, &end)) {
+       if (end == UV_MAX) {
+           Perl_dump_indent(aTHX_ level, file,
+                                       "%s[%"UVuf"] 0x%04"UVXf" .. INFINITY\n",
+                                   indent, (UV)count, start);
+       }
+       else if (end != start) {
+           Perl_dump_indent(aTHX_ level, file,
+                                    "%s[%"UVuf"] 0x%04"UVXf" .. 0x%04"UVXf"\n",
+                               indent, (UV)count, start,         end);
+       }
+       else {
+           Perl_dump_indent(aTHX_ level, file, "%s[%"UVuf"] 0x%04"UVXf"\n",
+                                            indent, (UV)count, start);
+       }
+        count += 2;
+    }
+}
+#endif
+
+#ifdef PERL_ARGS_ASSERT__INVLISTEQ
+bool
+S__invlistEQ(pTHX_ SV* const a, SV* const b, const bool complement_b)
+{
+    /* Return a boolean as to if the two passed in inversion lists are
+     * identical.  The final argument, if TRUE, says to take the complement of
+     * the second inversion list before doing the comparison */
+
+    const UV* array_a = invlist_array(a);
+    const UV* array_b = invlist_array(b);
+    UV len_a = _invlist_len(a);
+    UV len_b = _invlist_len(b);
+
+    UV i = 0;              /* current index into the arrays */
+    bool retval = TRUE;     /* Assume are identical until proven otherwise */
+
+    PERL_ARGS_ASSERT__INVLISTEQ;
+
+    /* If are to compare 'a' with the complement of b, set it
+     * up so are looking at b's complement. */
+    if (complement_b) {
+
+        /* The complement of nothing is everything, so <a> would have to have
+         * just one element, starting at zero (ending at infinity) */
+        if (len_b == 0) {
+            return (len_a == 1 && array_a[0] == 0);
+        }
+        else if (array_b[0] == 0) {
+
+            /* Otherwise, to complement, we invert.  Here, the first element is
+             * 0, just remove it.  To do this, we just pretend the array starts
+             * one later */
+
+            array_b++;
+            len_b--;
+        }
+        else {
+
+            /* But if the first element is not zero, we pretend the list starts
+             * at the 0 that is always stored immediately before the array. */
+            array_b--;
+            len_b++;
+        }
+    }
+
+    /* Make sure that the lengths are the same, as well as the final element
+     * before looping through the remainder.  (Thus we test the length, final,
+     * and first elements right off the bat) */
+    if (len_a != len_b || array_a[len_a-1] != array_b[len_a-1]) {
+        retval = FALSE;
+    }
+    else for (i = 0; i < len_a - 1; i++) {
+        if (array_a[i] != array_b[i]) {
+            retval = FALSE;
+            break;
+        }
+    }
+
+    return retval;
+}
+#endif
+
+#undef HEADER_LENGTH
+#undef TO_INTERNAL_SIZE
+#undef FROM_INTERNAL_SIZE
+#undef INVLIST_VERSION_ID
+
+/* End of inversion list object */
+
+STATIC void
+S_parse_lparen_question_flags(pTHX_ RExC_state_t *pRExC_state)
+{
+    /* This parses the flags that are in either the '(?foo)' or '(?foo:bar)'
+     * constructs, and updates RExC_flags with them.  On input, RExC_parse
+     * should point to the first flag; it is updated on output to point to the
+     * final ')' or ':'.  There needs to be at least one flag, or this will
+     * abort */
+
+    /* for (?g), (?gc), and (?o) warnings; warning
+       about (?c) will warn about (?g) -- japhy    */
+
+#define WASTED_O  0x01
+#define WASTED_G  0x02
+#define WASTED_C  0x04
+#define WASTED_GC (WASTED_G|WASTED_C)
+    I32 wastedflags = 0x00;
+    U32 posflags = 0, negflags = 0;
+    U32 *flagsp = &posflags;
+    char has_charset_modifier = '\0';
+    regex_charset cs;
+    bool has_use_defaults = FALSE;
+    const char* const seqstart = RExC_parse - 1; /* Point to the '?' */
+
+    PERL_ARGS_ASSERT_PARSE_LPAREN_QUESTION_FLAGS;
+
+    /* '^' as an initial flag sets certain defaults */
+    if (UCHARAT(RExC_parse) == '^') {
+        RExC_parse++;
+        has_use_defaults = TRUE;
+        STD_PMMOD_FLAGS_CLEAR(&RExC_flags);
+        set_regex_charset(&RExC_flags, (RExC_utf8 || RExC_uni_semantics)
+                                        ? REGEX_UNICODE_CHARSET
+                                        : REGEX_DEPENDS_CHARSET);
+    }
+
+    cs = get_regex_charset(RExC_flags);
+    if (cs == REGEX_DEPENDS_CHARSET
+        && (RExC_utf8 || RExC_uni_semantics))
+    {
+        cs = REGEX_UNICODE_CHARSET;
+    }
+
+    while (*RExC_parse) {
+        /* && strchr("iogcmsx", *RExC_parse) */
+        /* (?g), (?gc) and (?o) are useless here
+           and must be globally applied -- japhy */
+        switch (*RExC_parse) {
+
+            /* Code for the imsx flags */
+            CASE_STD_PMMOD_FLAGS_PARSE_SET(flagsp);
+
+            case LOCALE_PAT_MOD:
+                if (has_charset_modifier) {
+                    goto excess_modifier;
+                }
+                else if (flagsp == &negflags) {
+                    goto neg_modifier;
+                }
+                cs = REGEX_LOCALE_CHARSET;
+                has_charset_modifier = LOCALE_PAT_MOD;
+                break;
+            case UNICODE_PAT_MOD:
+                if (has_charset_modifier) {
+                    goto excess_modifier;
+                }
+                else if (flagsp == &negflags) {
+                    goto neg_modifier;
+                }
+                cs = REGEX_UNICODE_CHARSET;
+                has_charset_modifier = UNICODE_PAT_MOD;
+                break;
+            case ASCII_RESTRICT_PAT_MOD:
+                if (flagsp == &negflags) {
+                    goto neg_modifier;
+                }
+                if (has_charset_modifier) {
+                    if (cs != REGEX_ASCII_RESTRICTED_CHARSET) {
+                        goto excess_modifier;
+                    }
+                    /* Doubled modifier implies more restricted */
+                    cs = REGEX_ASCII_MORE_RESTRICTED_CHARSET;
+                }
+                else {
+                    cs = REGEX_ASCII_RESTRICTED_CHARSET;
+                }
+                has_charset_modifier = ASCII_RESTRICT_PAT_MOD;
+                break;
+            case DEPENDS_PAT_MOD:
+                if (has_use_defaults) {
+                    goto fail_modifiers;
+                }
+                else if (flagsp == &negflags) {
+                    goto neg_modifier;
+                }
+                else if (has_charset_modifier) {
+                    goto excess_modifier;
+                }
+
+                /* The dual charset means unicode semantics if the
+                 * pattern (or target, not known until runtime) are
+                 * utf8, or something in the pattern indicates unicode
+                 * semantics */
+                cs = (RExC_utf8 || RExC_uni_semantics)
+                     ? REGEX_UNICODE_CHARSET
+                     : REGEX_DEPENDS_CHARSET;
+                has_charset_modifier = DEPENDS_PAT_MOD;
+                break;
+            excess_modifier:
+                RExC_parse++;
+                if (has_charset_modifier == ASCII_RESTRICT_PAT_MOD) {
+                    vFAIL2("Regexp modifier \"%c\" may appear a maximum of twice", ASCII_RESTRICT_PAT_MOD);
+                }
+                else if (has_charset_modifier == *(RExC_parse - 1)) {
+                    vFAIL2("Regexp modifier \"%c\" may not appear twice",
+                                        *(RExC_parse - 1));
+                }
+                else {
+                    vFAIL3("Regexp modifiers \"%c\" and \"%c\" are mutually exclusive", has_charset_modifier, *(RExC_parse - 1));
+                }
+                /*NOTREACHED*/
+            neg_modifier:
+                RExC_parse++;
+                vFAIL2("Regexp modifier \"%c\" may not appear after the \"-\"",
+                                    *(RExC_parse - 1));
+                /*NOTREACHED*/
+            case ONCE_PAT_MOD: /* 'o' */
+            case GLOBAL_PAT_MOD: /* 'g' */
+                if (SIZE_ONLY && ckWARN(WARN_REGEXP)) {
+                    const I32 wflagbit = *RExC_parse == 'o'
+                                         ? WASTED_O
+                                         : WASTED_G;
+                    if (! (wastedflags & wflagbit) ) {
+                        wastedflags |= wflagbit;
+                       /* diag_listed_as: Useless (?-%s) - don't use /%s modifier in regex; marked by <-- HERE in m/%s/ */
+                        vWARN5(
+                            RExC_parse + 1,
+                            "Useless (%s%c) - %suse /%c modifier",
+                            flagsp == &negflags ? "?-" : "?",
+                            *RExC_parse,
+                            flagsp == &negflags ? "don't " : "",
+                            *RExC_parse
+                        );
+                    }
+                }
+                break;
+
+            case CONTINUE_PAT_MOD: /* 'c' */
+                if (SIZE_ONLY && ckWARN(WARN_REGEXP)) {
+                    if (! (wastedflags & WASTED_C) ) {
+                        wastedflags |= WASTED_GC;
+                       /* diag_listed_as: Useless (?-%s) - don't use /%s modifier in regex; marked by <-- HERE in m/%s/ */
+                        vWARN3(
+                            RExC_parse + 1,
+                            "Useless (%sc) - %suse /gc modifier",
+                            flagsp == &negflags ? "?-" : "?",
+                            flagsp == &negflags ? "don't " : ""
+                        );
+                    }
+                }
+                break;
+            case KEEPCOPY_PAT_MOD: /* 'p' */
+                if (flagsp == &negflags) {
+                    if (SIZE_ONLY)
+                        ckWARNreg(RExC_parse + 1,"Useless use of (?-p)");
+                } else {
+                    *flagsp |= RXf_PMf_KEEPCOPY;
+                }
+                break;
+            case '-':
+                /* A flag is a default iff it is following a minus, so
+                 * if there is a minus, it means will be trying to
+                 * re-specify a default which is an error */
+                if (has_use_defaults || flagsp == &negflags) {
+                    goto fail_modifiers;
+                }
+                flagsp = &negflags;
+                wastedflags = 0;  /* reset so (?g-c) warns twice */
+                break;
+            case ':':
+            case ')':
+                RExC_flags |= posflags;
+                RExC_flags &= ~negflags;
+                set_regex_charset(&RExC_flags, cs);
+                if (RExC_flags & RXf_PMf_FOLD) {
+                    RExC_contains_i = 1;
+                }
+                return;
+                /*NOTREACHED*/
+            default:
+            fail_modifiers:
+                RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
+               /* diag_listed_as: Sequence (?%s...) not recognized in regex; marked by <-- HERE in m/%s/ */
+                vFAIL2utf8f("Sequence (%"UTF8f"...) not recognized",
+                      UTF8fARG(UTF, RExC_parse-seqstart, seqstart));
+                /*NOTREACHED*/
+        }
+
+        ++RExC_parse;
+    }
+}
+
+/*
+ - reg - regular expression, i.e. main body or parenthesized thing
+ *
+ * Caller must absorb opening parenthesis.
+ *
+ * Combining parenthesis handling with the base level of regular expression
+ * is a trifle forced, but the need to tie the tails of the branches to what
+ * follows makes it hard to avoid.
+ */
+#define REGTAIL(x,y,z) regtail((x),(y),(z),depth+1)
+#ifdef DEBUGGING
+#define REGTAIL_STUDY(x,y,z) regtail_study((x),(y),(z),depth+1)
+#else
+#define REGTAIL_STUDY(x,y,z) regtail((x),(y),(z),depth+1)
+#endif
+
+/* Returns NULL, setting *flagp to TRYAGAIN at the end of (?) that only sets
+   flags. Returns NULL, setting *flagp to RESTART_UTF8 if the sizing scan
+   needs to be restarted.
+   Otherwise would only return NULL if regbranch() returns NULL, which
+   cannot happen.  */
+STATIC regnode *
+S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
+    /* paren: Parenthesized? 0=top; 1,2=inside '(': changed to letter.
+     * 2 is like 1, but indicates that nextchar() has been called to advance
+     * RExC_parse beyond the '('.  Things like '(?' are indivisible tokens, and
+     * this flag alerts us to the need to check for that */
+{
+    dVAR;
+    regnode *ret;              /* Will be the head of the group. */
+    regnode *br;
+    regnode *lastbr;
+    regnode *ender = NULL;
+    I32 parno = 0;
+    I32 flags;
+    U32 oregflags = RExC_flags;
+    bool have_branch = 0;
+    bool is_open = 0;
+    I32 freeze_paren = 0;
+    I32 after_freeze = 0;
+
+    char * parse_start = RExC_parse; /* MJD */
+    char * const oregcomp_parse = RExC_parse;
+
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REG;
+    DEBUG_PARSE("reg ");
+
+    *flagp = 0;                                /* Tentatively. */
+
+
+    /* Make an OPEN node, if parenthesized. */
+    if (paren) {
+
+        /* Under /x, space and comments can be gobbled up between the '(' and
+         * here (if paren ==2).  The forms '(*VERB' and '(?...' disallow such
+         * intervening space, as the sequence is a token, and a token should be
+         * indivisible */
+        bool has_intervening_patws = paren == 2 && *(RExC_parse - 1) != '(';
+
+        if ( *RExC_parse == '*') { /* (*VERB:ARG) */
+           char *start_verb = RExC_parse;
+           STRLEN verb_len = 0;
+           char *start_arg = NULL;
+           unsigned char op = 0;
+           int argok = 1;
+            int internal_argval = 0; /* internal_argval is only useful if
+                                        !argok */
+
+            if (has_intervening_patws && SIZE_ONLY) {
+                ckWARNregdep(RExC_parse + 1, "In '(*VERB...)', splitting the initial '(*' is deprecated");
+            }
+           while ( *RExC_parse && *RExC_parse != ')' ) {
+               if ( *RExC_parse == ':' ) {
+                   start_arg = RExC_parse + 1;
+                   break;
+               }
+               RExC_parse++;
+           }
+           ++start_verb;
+           verb_len = RExC_parse - start_verb;
+           if ( start_arg ) {
+               RExC_parse++;
+               while ( *RExC_parse && *RExC_parse != ')' )
+                   RExC_parse++;
+               if ( *RExC_parse != ')' )
+                   vFAIL("Unterminated verb pattern argument");
+               if ( RExC_parse == start_arg )
+                   start_arg = NULL;
+           } else {
+               if ( *RExC_parse != ')' )
+                   vFAIL("Unterminated verb pattern");
+           }
+
+           switch ( *start_verb ) {
+            case 'A':  /* (*ACCEPT) */
+                if ( memEQs(start_verb,verb_len,"ACCEPT") ) {
+                   op = ACCEPT;
+                   internal_argval = RExC_nestroot;
+               }
+               break;
+            case 'C':  /* (*COMMIT) */
+                if ( memEQs(start_verb,verb_len,"COMMIT") )
+                    op = COMMIT;
+                break;
+            case 'F':  /* (*FAIL) */
+                if ( verb_len==1 || memEQs(start_verb,verb_len,"FAIL") ) {
+                   op = OPFAIL;
+                   argok = 0;
+               }
+               break;
+            case ':':  /* (*:NAME) */
+           case 'M':  /* (*MARK:NAME) */
+               if ( verb_len==0 || memEQs(start_verb,verb_len,"MARK") ) {
+                    op = MARKPOINT;
+                    argok = -1;
+                }
+                break;
+            case 'P':  /* (*PRUNE) */
+                if ( memEQs(start_verb,verb_len,"PRUNE") )
+                    op = PRUNE;
+                break;
+            case 'S':   /* (*SKIP) */
+                if ( memEQs(start_verb,verb_len,"SKIP") )
+                    op = SKIP;
+                break;
+            case 'T':  /* (*THEN) */
+                /* [19:06] <TimToady> :: is then */
+                if ( memEQs(start_verb,verb_len,"THEN") ) {
+                    op = CUTGROUP;
+                    RExC_seen |= REG_CUTGROUP_SEEN;
+                }
+                break;
+           }
+           if ( ! op ) {
+               RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
+                vFAIL2utf8f(
+                    "Unknown verb pattern '%"UTF8f"'",
+                    UTF8fARG(UTF, verb_len, start_verb));
+           }
+           if ( argok ) {
+                if ( start_arg && internal_argval ) {
+                   vFAIL3("Verb pattern '%.*s' may not have an argument",
+                       verb_len, start_verb);
+               } else if ( argok < 0 && !start_arg ) {
+                    vFAIL3("Verb pattern '%.*s' has a mandatory argument",
+                       verb_len, start_verb);
+               } else {
+                   ret = reganode(pRExC_state, op, internal_argval);
+                   if ( ! internal_argval && ! SIZE_ONLY ) {
+                        if (start_arg) {
+                            SV *sv = newSVpvn( start_arg,
+                                               RExC_parse - start_arg);
+                            ARG(ret) = add_data( pRExC_state,
+                                                 STR_WITH_LEN("S"));
+                            RExC_rxi->data->data[ARG(ret)]=(void*)sv;
+                            ret->flags = 0;
+                        } else {
+                            ret->flags = 1;
+                        }
+                    }
+               }
+               if (!internal_argval)
+                    RExC_seen |= REG_VERBARG_SEEN;
+           } else if ( start_arg ) {
+               vFAIL3("Verb pattern '%.*s' may not have an argument",
+                       verb_len, start_verb);
+           } else {
+               ret = reg_node(pRExC_state, op);
+           }
+           nextchar(pRExC_state);
+           return ret;
+        }
+        else if (*RExC_parse == '?') { /* (?...) */
+           bool is_logical = 0;
+           const char * const seqstart = RExC_parse;
+            if (has_intervening_patws && SIZE_ONLY) {
+                ckWARNregdep(RExC_parse + 1, "In '(?...)', splitting the initial '(?' is deprecated");
+            }
+
+           RExC_parse++;
+           paren = *RExC_parse++;
+           ret = NULL;                 /* For look-ahead/behind. */
+           switch (paren) {
+
+           case 'P':   /* (?P...) variants for those used to PCRE/Python */
+               paren = *RExC_parse++;
+               if ( paren == '<')         /* (?P<...>) named capture */
+                   goto named_capture;
+                else if (paren == '>') {   /* (?P>name) named recursion */
+                    goto named_recursion;
+                }
+                else if (paren == '=') {   /* (?P=...)  named backref */
+                    /* this pretty much dupes the code for \k<NAME> in
+                     * regatom(), if you change this make sure you change that
+                     * */
+                    char* name_start = RExC_parse;
+                   U32 num = 0;
+                    SV *sv_dat = reg_scan_name(pRExC_state,
+                        SIZE_ONLY ? REG_RSN_RETURN_NULL : REG_RSN_RETURN_DATA);
+                    if (RExC_parse == name_start || *RExC_parse != ')')
+                        /* diag_listed_as: Sequence ?P=... not terminated in regex; marked by <-- HERE in m/%s/ */
+                        vFAIL2("Sequence %.3s... not terminated",parse_start);
+
+                    if (!SIZE_ONLY) {
+                        num = add_data( pRExC_state, STR_WITH_LEN("S"));
+                        RExC_rxi->data->data[num]=(void*)sv_dat;
+                        SvREFCNT_inc_simple_void(sv_dat);
+                    }
+                    RExC_sawback = 1;
+                   ret = reganode(pRExC_state,
+                                  ((! FOLD)
+                                    ? NREF
+                                    : (ASCII_FOLD_RESTRICTED)
+                                      ? NREFFA
+                                       : (AT_LEAST_UNI_SEMANTICS)
+                                         ? NREFFU
+                                         : (LOC)
+                                           ? NREFFL
+                                           : NREFF),
+                                   num);
+                    *flagp |= HASWIDTH;
+
+                    Set_Node_Offset(ret, parse_start+1);
+                    Set_Node_Cur_Length(ret, parse_start);
+
+                    nextchar(pRExC_state);
+                    return ret;
+                }
+                RExC_parse++;
+                /* diag_listed_as: Sequence (?%s...) not recognized in regex; marked by <-- HERE in m/%s/ */
+               vFAIL3("Sequence (%.*s...) not recognized",
+                                RExC_parse-seqstart, seqstart);
+               /*NOTREACHED*/
+            case '<':           /* (?<...) */
+               if (*RExC_parse == '!')
+                   paren = ',';
+               else if (*RExC_parse != '=')
+              named_capture:
+               {               /* (?<...>) */
+                   char *name_start;
+                   SV *svname;
+                   paren= '>';
+            case '\'':          /* (?'...') */
+                   name_start= RExC_parse;
+                   svname = reg_scan_name(pRExC_state,
+                        SIZE_ONLY    /* reverse test from the others */
+                        ? REG_RSN_RETURN_NAME
+                        : REG_RSN_RETURN_NULL);
+                   if (RExC_parse == name_start || *RExC_parse != paren)
+                       vFAIL2("Sequence (?%c... not terminated",
+                           paren=='>' ? '<' : paren);
+                   if (SIZE_ONLY) {
+                       HE *he_str;
+                       SV *sv_dat = NULL;
+                        if (!svname) /* shouldn't happen */
+                            Perl_croak(aTHX_
+                                "panic: reg_scan_name returned NULL");
+                        if (!RExC_paren_names) {
+                            RExC_paren_names= newHV();
+                            sv_2mortal(MUTABLE_SV(RExC_paren_names));
+#ifdef DEBUGGING
+                            RExC_paren_name_list= newAV();
+                            sv_2mortal(MUTABLE_SV(RExC_paren_name_list));
+#endif
+                        }
+                        he_str = hv_fetch_ent( RExC_paren_names, svname, 1, 0 );
+                        if ( he_str )
+                            sv_dat = HeVAL(he_str);
+                        if ( ! sv_dat ) {
+                            /* croak baby croak */
+                            Perl_croak(aTHX_
+                                "panic: paren_name hash element allocation failed");
+                        } else if ( SvPOK(sv_dat) ) {
+                            /* (?|...) can mean we have dupes so scan to check
+                               its already been stored. Maybe a flag indicating
+                               we are inside such a construct would be useful,
+                               but the arrays are likely to be quite small, so
+                               for now we punt -- dmq */
+                            IV count = SvIV(sv_dat);
+                            I32 *pv = (I32*)SvPVX(sv_dat);
+                            IV i;
+                            for ( i = 0 ; i < count ; i++ ) {
+                                if ( pv[i] == RExC_npar ) {
+                                    count = 0;
+                                    break;
+                                }
+                            }
+                            if ( count ) {
+                                pv = (I32*)SvGROW(sv_dat,
+                                                SvCUR(sv_dat) + sizeof(I32)+1);
+                                SvCUR_set(sv_dat, SvCUR(sv_dat) + sizeof(I32));
+                                pv[count] = RExC_npar;
+                                SvIV_set(sv_dat, SvIVX(sv_dat) + 1);
+                            }
+                        } else {
+                            (void)SvUPGRADE(sv_dat,SVt_PVNV);
+                            sv_setpvn(sv_dat, (char *)&(RExC_npar),
+                                                                sizeof(I32));
+                            SvIOK_on(sv_dat);
+                            SvIV_set(sv_dat, 1);
+                        }
+#ifdef DEBUGGING
+                        /* Yes this does cause a memory leak in debugging Perls
+                         * */
+                        if (!av_store(RExC_paren_name_list,
+                                      RExC_npar, SvREFCNT_inc(svname)))
+                            SvREFCNT_dec_NN(svname);
+#endif
+
+                        /*sv_dump(sv_dat);*/
+                    }
+                    nextchar(pRExC_state);
+                   paren = 1;
+                   goto capturing_parens;
+               }
+                RExC_seen |= REG_LOOKBEHIND_SEEN;
+               RExC_in_lookbehind++;
+               RExC_parse++;
+           case '=':           /* (?=...) */
+               RExC_seen_zerolen++;
+                break;
+           case '!':           /* (?!...) */
+               RExC_seen_zerolen++;
+               if (*RExC_parse == ')') {
+                   ret=reg_node(pRExC_state, OPFAIL);
+                   nextchar(pRExC_state);
+                   return ret;
+               }
+               break;
+           case '|':           /* (?|...) */
+               /* branch reset, behave like a (?:...) except that
+                  buffers in alternations share the same numbers */
+               paren = ':';
+               after_freeze = freeze_paren = RExC_npar;
+               break;
+           case ':':           /* (?:...) */
+           case '>':           /* (?>...) */
+               break;
+           case '$':           /* (?$...) */
+           case '@':           /* (?@...) */
+               vFAIL2("Sequence (?%c...) not implemented", (int)paren);
+               break;
+            case '#':           /* (?#...) */
+                /* XXX As soon as we disallow separating the '?' and '*' (by
+                 * spaces or (?#...) comment), it is believed that this case
+                 * will be unreachable and can be removed.  See
+                 * [perl #117327] */
+                while (*RExC_parse && *RExC_parse != ')')
+                   RExC_parse++;
+               if (*RExC_parse != ')')
+                   FAIL("Sequence (?#... not terminated");
+               nextchar(pRExC_state);
+               *flagp = TRYAGAIN;
+               return NULL;
+           case '0' :           /* (?0) */
+           case 'R' :           /* (?R) */
+               if (*RExC_parse != ')')
+                   FAIL("Sequence (?R) not terminated");
+               ret = reg_node(pRExC_state, GOSTART);
+                    RExC_seen |= REG_GOSTART_SEEN;
+               *flagp |= POSTPONED;
+               nextchar(pRExC_state);
+               return ret;
+               /*notreached*/
+            { /* named and numeric backreferences */
+                I32 num;
+            case '&':            /* (?&NAME) */
+                parse_start = RExC_parse - 1;
+              named_recursion:
+                {
+                   SV *sv_dat = reg_scan_name(pRExC_state,
+                       SIZE_ONLY ? REG_RSN_RETURN_NULL : REG_RSN_RETURN_DATA);
+                    num = sv_dat ? *((I32 *)SvPVX(sv_dat)) : 0;
+                }
+                if (RExC_parse == RExC_end || *RExC_parse != ')')
+                    vFAIL("Sequence (?&... not terminated");
+                goto gen_recurse_regop;
+                assert(0); /* NOT REACHED */
+            case '+':
+                if (!(RExC_parse[0] >= '1' && RExC_parse[0] <= '9')) {
+                    RExC_parse++;
+                    vFAIL("Illegal pattern");
+                }
+                goto parse_recursion;
+                /* NOT REACHED*/
+            case '-': /* (?-1) */
+                if (!(RExC_parse[0] >= '1' && RExC_parse[0] <= '9')) {
+                    RExC_parse--; /* rewind to let it be handled later */
+                    goto parse_flags;
+                }
+                /*FALLTHROUGH */
+            case '1': case '2': case '3': case '4': /* (?1) */
+           case '5': case '6': case '7': case '8': case '9':
+               RExC_parse--;
+              parse_recursion:
+               num = atoi(RExC_parse);
+               parse_start = RExC_parse - 1; /* MJD */
+               if (*RExC_parse == '-')
+                   RExC_parse++;
+               while (isDIGIT(*RExC_parse))
+                       RExC_parse++;
+               if (*RExC_parse!=')')
+                   vFAIL("Expecting close bracket");
+
+              gen_recurse_regop:
+                if ( paren == '-' ) {
+                    /*
+                    Diagram of capture buffer numbering.
+                    Top line is the normal capture buffer numbers
+                    Bottom line is the negative indexing as from
+                    the X (the (?-2))
+
+                    +   1 2    3 4 5 X          6 7
+                       /(a(x)y)(a(b(c(?-2)d)e)f)(g(h))/
+                    -   5 4    3 2 1 X          x x
+
+                    */
+                    num = RExC_npar + num;
+                    if (num < 1)  {
+                        RExC_parse++;
+                        vFAIL("Reference to nonexistent group");
+                    }
+                } else if ( paren == '+' ) {
+                    num = RExC_npar + num - 1;
+                }
+
+                ret = reganode(pRExC_state, GOSUB, num);
+                if (!SIZE_ONLY) {
+                   if (num > (I32)RExC_rx->nparens) {
+                       RExC_parse++;
+                       vFAIL("Reference to nonexistent group");
+                   }
+                   ARG2L_SET( ret, RExC_recurse_count++);
+                    RExC_emit++;
+                   DEBUG_OPTIMISE_MORE_r(PerlIO_printf(Perl_debug_log,
+                       "Recurse #%"UVuf" to %"IVdf"\n",
+                              (UV)ARG(ret), (IV)ARG2L(ret)));
+               } else {
+                   RExC_size++;
+               }
+                    RExC_seen |= REG_RECURSE_SEEN;
+                Set_Node_Length(ret, 1 + regarglen[OP(ret)]); /* MJD */
+               Set_Node_Offset(ret, parse_start); /* MJD */
+
+                *flagp |= POSTPONED;
+                nextchar(pRExC_state);
+                return ret;
+            } /* named and numeric backreferences */
+            assert(0); /* NOT REACHED */
+
+           case '?':           /* (??...) */
+               is_logical = 1;
+               if (*RExC_parse != '{') {
+                   RExC_parse++;
+                    /* diag_listed_as: Sequence (?%s...) not recognized in regex; marked by <-- HERE in m/%s/ */
+                    vFAIL2utf8f(
+                        "Sequence (%"UTF8f"...) not recognized",
+                        UTF8fARG(UTF, RExC_parse-seqstart, seqstart));
+                   /*NOTREACHED*/
+               }
+               *flagp |= POSTPONED;
+               paren = *RExC_parse++;
+               /* FALL THROUGH */
+           case '{':           /* (?{...}) */
+           {
+               U32 n = 0;
+               struct reg_code_block *cb;
+
+               RExC_seen_zerolen++;
+
+               if (   !pRExC_state->num_code_blocks
+                   || pRExC_state->code_index >= pRExC_state->num_code_blocks
+                   || pRExC_state->code_blocks[pRExC_state->code_index].start
+                       != (STRLEN)((RExC_parse -3 - (is_logical ? 1 : 0))
+                           - RExC_start)
+               ) {
+                   if (RExC_pm_flags & PMf_USE_RE_EVAL)
+                       FAIL("panic: Sequence (?{...}): no code block found\n");
+                   FAIL("Eval-group not allowed at runtime, use re 'eval'");
+               }
+               /* this is a pre-compiled code block (?{...}) */
+               cb = &pRExC_state->code_blocks[pRExC_state->code_index];
+               RExC_parse = RExC_start + cb->end;
+               if (!SIZE_ONLY) {
+                   OP *o = cb->block;
+                   if (cb->src_regex) {
+                       n = add_data(pRExC_state, STR_WITH_LEN("rl"));
+                       RExC_rxi->data->data[n] =
+                           (void*)SvREFCNT_inc((SV*)cb->src_regex);
+                       RExC_rxi->data->data[n+1] = (void*)o;
+                   }
+                   else {
+                       n = add_data(pRExC_state,
+                              (RExC_pm_flags & PMf_HAS_CV) ? "L" : "l", 1);
+                       RExC_rxi->data->data[n] = (void*)o;
+                   }
+               }
+               pRExC_state->code_index++;
+               nextchar(pRExC_state);
+
+               if (is_logical) {
+                    regnode *eval;
+                   ret = reg_node(pRExC_state, LOGICAL);
+                    eval = reganode(pRExC_state, EVAL, n);
+                   if (!SIZE_ONLY) {
+                       ret->flags = 2;
+                        /* for later propagation into (??{}) return value */
+                        eval->flags = (U8) (RExC_flags & RXf_PMf_COMPILETIME);
+                    }
+                    REGTAIL(pRExC_state, ret, eval);
+                    /* deal with the length of this later - MJD */
+                   return ret;
+               }
+               ret = reganode(pRExC_state, EVAL, n);
+               Set_Node_Length(ret, RExC_parse - parse_start + 1);
+               Set_Node_Offset(ret, parse_start);
+               return ret;
+           }
+           case '(':           /* (?(?{...})...) and (?(?=...)...) */
+           {
+               int is_define= 0;
+               if (RExC_parse[0] == '?') {        /* (?(?...)) */
+                   if (RExC_parse[1] == '=' || RExC_parse[1] == '!'
+                       || RExC_parse[1] == '<'
+                       || RExC_parse[1] == '{') { /* Lookahead or eval. */
+                       I32 flag;
+                        regnode *tail;
+
+                       ret = reg_node(pRExC_state, LOGICAL);
+                       if (!SIZE_ONLY)
+                           ret->flags = 1;
+
+                        tail = reg(pRExC_state, 1, &flag, depth+1);
+                        if (flag & RESTART_UTF8) {
+                            *flagp = RESTART_UTF8;
+                            return NULL;
+                        }
+                        REGTAIL(pRExC_state, ret, tail);
+                       goto insert_if;
+                   }
+               }
+               else if ( RExC_parse[0] == '<'     /* (?(<NAME>)...) */
+                        || RExC_parse[0] == '\'' ) /* (?('NAME')...) */
+               {
+                   char ch = RExC_parse[0] == '<' ? '>' : '\'';
+                   char *name_start= RExC_parse++;
+                   U32 num = 0;
+                   SV *sv_dat=reg_scan_name(pRExC_state,
+                       SIZE_ONLY ? REG_RSN_RETURN_NULL : REG_RSN_RETURN_DATA);
+                   if (RExC_parse == name_start || *RExC_parse != ch)
+                        vFAIL2("Sequence (?(%c... not terminated",
+                            (ch == '>' ? '<' : ch));
+                    RExC_parse++;
+                   if (!SIZE_ONLY) {
+                        num = add_data( pRExC_state, STR_WITH_LEN("S"));
+                        RExC_rxi->data->data[num]=(void*)sv_dat;
+                        SvREFCNT_inc_simple_void(sv_dat);
+                    }
+                    ret = reganode(pRExC_state,NGROUPP,num);
+                    goto insert_if_check_paren;
+               }
+               else if (RExC_parse[0] == 'D' &&
+                        RExC_parse[1] == 'E' &&
+                        RExC_parse[2] == 'F' &&
+                        RExC_parse[3] == 'I' &&
+                        RExC_parse[4] == 'N' &&
+                        RExC_parse[5] == 'E')
+               {
+                   ret = reganode(pRExC_state,DEFINEP,0);
+                   RExC_parse +=6 ;
+                   is_define = 1;
+                   goto insert_if_check_paren;
+               }
+               else if (RExC_parse[0] == 'R') {
+                   RExC_parse++;
+                   parno = 0;
+                   if (RExC_parse[0] >= '1' && RExC_parse[0] <= '9' ) {
+                       parno = atoi(RExC_parse++);
+                       while (isDIGIT(*RExC_parse))
+                           RExC_parse++;
+                   } else if (RExC_parse[0] == '&') {
+                       SV *sv_dat;
+                       RExC_parse++;
+                       sv_dat = reg_scan_name(pRExC_state,
+                            SIZE_ONLY
+                            ? REG_RSN_RETURN_NULL
+                            : REG_RSN_RETURN_DATA);
+                       parno = sv_dat ? *((I32 *)SvPVX(sv_dat)) : 0;
+                   }
+                   ret = reganode(pRExC_state,INSUBP,parno);
+                   goto insert_if_check_paren;
+               }
+               else if (RExC_parse[0] >= '1' && RExC_parse[0] <= '9' ) {
+                    /* (?(1)...) */
+                   char c;
+                   char *tmp;
+                   parno = atoi(RExC_parse++);
+
+                   while (isDIGIT(*RExC_parse))
+                       RExC_parse++;
+                    ret = reganode(pRExC_state, GROUPP, parno);
+
+                 insert_if_check_paren:
+                   if (*(tmp = nextchar(pRExC_state)) != ')') {
+                        /* nextchar also skips comments, so undo its work
+                         * and skip over the the next character.
+                         */
+                        RExC_parse = tmp;
+                        RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
+                       vFAIL("Switch condition not recognized");
+                   }
+                 insert_if:
+                    REGTAIL(pRExC_state, ret, reganode(pRExC_state, IFTHEN, 0));
+                    br = regbranch(pRExC_state, &flags, 1,depth+1);
+                   if (br == NULL) {
+                        if (flags & RESTART_UTF8) {
+                            *flagp = RESTART_UTF8;
+                            return NULL;
+                        }
+                        FAIL2("panic: regbranch returned NULL, flags=%#"UVxf"",
+                              (UV) flags);
+                    } else
+                        REGTAIL(pRExC_state, br, reganode(pRExC_state,
+                                                          LONGJMP, 0));
+                   c = *nextchar(pRExC_state);
+                   if (flags&HASWIDTH)
+                       *flagp |= HASWIDTH;
+                   if (c == '|') {
+                       if (is_define)
+                           vFAIL("(?(DEFINE)....) does not allow branches");
+
+                        /* Fake one for optimizer.  */
+                        lastbr = reganode(pRExC_state, IFTHEN, 0);
+
+                        if (!regbranch(pRExC_state, &flags, 1,depth+1)) {
+                            if (flags & RESTART_UTF8) {
+                                *flagp = RESTART_UTF8;
+                                return NULL;
+                            }
+                            FAIL2("panic: regbranch returned NULL, flags=%#"UVxf"",
+                                  (UV) flags);
+                        }
+                        REGTAIL(pRExC_state, ret, lastbr);
+                       if (flags&HASWIDTH)
+                           *flagp |= HASWIDTH;
+                       c = *nextchar(pRExC_state);
+                   }
+                   else
+                       lastbr = NULL;
+                   if (c != ')')
+                       vFAIL("Switch (?(condition)... contains too many branches");
+                   ender = reg_node(pRExC_state, TAIL);
+                    REGTAIL(pRExC_state, br, ender);
+                   if (lastbr) {
+                        REGTAIL(pRExC_state, lastbr, ender);
+                        REGTAIL(pRExC_state, NEXTOPER(NEXTOPER(lastbr)), ender);
+                   }
+                   else
+                        REGTAIL(pRExC_state, ret, ender);
+                    RExC_size++; /* XXX WHY do we need this?!!
+                                    For large programs it seems to be required
+                                    but I can't figure out why. -- dmq*/
+                   return ret;
+               }
+               else {
+                    RExC_parse += UTF ? UTF8SKIP(RExC_parse) : 1;
+                    vFAIL("Unknown switch condition (?(...))");
+               }
+           }
+           case '[':           /* (?[ ... ]) */
+                return handle_regex_sets(pRExC_state, NULL, flagp, depth,
+                                         oregcomp_parse);
+            case 0:
+               RExC_parse--; /* for vFAIL to print correctly */
+                vFAIL("Sequence (? incomplete");
+                break;
+           default: /* e.g., (?i) */
+               --RExC_parse;
+              parse_flags:
+               parse_lparen_question_flags(pRExC_state);
+                if (UCHARAT(RExC_parse) != ':') {
+                    nextchar(pRExC_state);
+                    *flagp = TRYAGAIN;
+                    return NULL;
+                }
+                paren = ':';
+                nextchar(pRExC_state);
+                ret = NULL;
+                goto parse_rest;
+            } /* end switch */
+       }
+       else {                  /* (...) */
+         capturing_parens:
+           parno = RExC_npar;
+           RExC_npar++;
+
+           ret = reganode(pRExC_state, OPEN, parno);
+           if (!SIZE_ONLY ){
+               if (!RExC_nestroot)
+                   RExC_nestroot = parno;
+                if (RExC_seen & REG_RECURSE_SEEN
+                   && !RExC_open_parens[parno-1])
+               {
+                   DEBUG_OPTIMISE_MORE_r(PerlIO_printf(Perl_debug_log,
+                       "Setting open paren #%"IVdf" to %d\n",
+                       (IV)parno, REG_NODE_NUM(ret)));
+                   RExC_open_parens[parno-1]= ret;
+               }
+           }
+            Set_Node_Length(ret, 1); /* MJD */
+            Set_Node_Offset(ret, RExC_parse); /* MJD */
+           is_open = 1;
+       }
+    }
+    else                        /* ! paren */
+       ret = NULL;
+
+   parse_rest:
+    /* Pick up the branches, linking them together. */
+    parse_start = RExC_parse;   /* MJD */
+    br = regbranch(pRExC_state, &flags, 1,depth+1);
+
+    /*     branch_len = (paren != 0); */
+
+    if (br == NULL) {
+        if (flags & RESTART_UTF8) {
+            *flagp = RESTART_UTF8;
+            return NULL;
+        }
+        FAIL2("panic: regbranch returned NULL, flags=%#"UVxf"", (UV) flags);
+    }
+    if (*RExC_parse == '|') {
+       if (!SIZE_ONLY && RExC_extralen) {
+           reginsert(pRExC_state, BRANCHJ, br, depth+1);
+       }
+       else {                  /* MJD */
+           reginsert(pRExC_state, BRANCH, br, depth+1);
+            Set_Node_Length(br, paren != 0);
+            Set_Node_Offset_To_R(br-RExC_emit_start, parse_start-RExC_start);
+        }
+       have_branch = 1;
+       if (SIZE_ONLY)
+           RExC_extralen += 1;         /* For BRANCHJ-BRANCH. */
+    }
+    else if (paren == ':') {
+       *flagp |= flags&SIMPLE;
+    }
+    if (is_open) {                             /* Starts with OPEN. */
+        REGTAIL(pRExC_state, ret, br);          /* OPEN -> first. */
+    }
+    else if (paren != '?')             /* Not Conditional */
+       ret = br;
+    *flagp |= flags & (SPSTART | HASWIDTH | POSTPONED);
+    lastbr = br;
+    while (*RExC_parse == '|') {
+       if (!SIZE_ONLY && RExC_extralen) {
+           ender = reganode(pRExC_state, LONGJMP,0);
+
+            /* Append to the previous. */
+            REGTAIL(pRExC_state, NEXTOPER(NEXTOPER(lastbr)), ender);
+       }
+       if (SIZE_ONLY)
+           RExC_extralen += 2;         /* Account for LONGJMP. */
+       nextchar(pRExC_state);
+       if (freeze_paren) {
+           if (RExC_npar > after_freeze)
+               after_freeze = RExC_npar;
+            RExC_npar = freeze_paren;
+        }
+        br = regbranch(pRExC_state, &flags, 0, depth+1);
+
+       if (br == NULL) {
+            if (flags & RESTART_UTF8) {
+                *flagp = RESTART_UTF8;
+                return NULL;
+            }
+            FAIL2("panic: regbranch returned NULL, flags=%#"UVxf"", (UV) flags);
+        }
+        REGTAIL(pRExC_state, lastbr, br);               /* BRANCH -> BRANCH. */
+       lastbr = br;
+       *flagp |= flags & (SPSTART | HASWIDTH | POSTPONED);
+    }
+
+    if (have_branch || paren != ':') {
+       /* Make a closing node, and hook it on the end. */
+       switch (paren) {
+       case ':':
+           ender = reg_node(pRExC_state, TAIL);
+           break;
+       case 1: case 2:
+           ender = reganode(pRExC_state, CLOSE, parno);
+            if (!SIZE_ONLY && RExC_seen & REG_RECURSE_SEEN) {
+               DEBUG_OPTIMISE_MORE_r(PerlIO_printf(Perl_debug_log,
+                       "Setting close paren #%"IVdf" to %d\n",
+                       (IV)parno, REG_NODE_NUM(ender)));
+               RExC_close_parens[parno-1]= ender;
+               if (RExC_nestroot == parno)
+                   RExC_nestroot = 0;
+           }
+            Set_Node_Offset(ender,RExC_parse+1); /* MJD */
+            Set_Node_Length(ender,1); /* MJD */
+           break;
+       case '<':
+       case ',':
+       case '=':
+       case '!':
+           *flagp &= ~HASWIDTH;
+           /* FALL THROUGH */
+       case '>':
+           ender = reg_node(pRExC_state, SUCCEED);
+           break;
+       case 0:
+           ender = reg_node(pRExC_state, END);
+           if (!SIZE_ONLY) {
+                assert(!RExC_opend); /* there can only be one! */
+                RExC_opend = ender;
+            }
+           break;
+       }
+        DEBUG_PARSE_r(if (!SIZE_ONLY) {
+            SV * const mysv_val1=sv_newmortal();
+            SV * const mysv_val2=sv_newmortal();
+            DEBUG_PARSE_MSG("lsbr");
+            regprop(RExC_rx, mysv_val1, lastbr, NULL);
+            regprop(RExC_rx, mysv_val2, ender, NULL);
+            PerlIO_printf(Perl_debug_log, "~ tying lastbr %s (%"IVdf") to ender %s (%"IVdf") offset %"IVdf"\n",
+                          SvPV_nolen_const(mysv_val1),
+                          (IV)REG_NODE_NUM(lastbr),
+                          SvPV_nolen_const(mysv_val2),
+                          (IV)REG_NODE_NUM(ender),
+                          (IV)(ender - lastbr)
+            );
+        });
+        REGTAIL(pRExC_state, lastbr, ender);
+
+       if (have_branch && !SIZE_ONLY) {
+            char is_nothing= 1;
+           if (depth==1)
+                RExC_seen |= REG_TOP_LEVEL_BRANCHES_SEEN;
+
+           /* Hook the tails of the branches to the closing node. */
+           for (br = ret; br; br = regnext(br)) {
+               const U8 op = PL_regkind[OP(br)];
+               if (op == BRANCH) {
+                    REGTAIL_STUDY(pRExC_state, NEXTOPER(br), ender);
+                    if ( OP(NEXTOPER(br)) != NOTHING
+                         || regnext(NEXTOPER(br)) != ender)
+                        is_nothing= 0;
+               }
+               else if (op == BRANCHJ) {
+                    REGTAIL_STUDY(pRExC_state, NEXTOPER(NEXTOPER(br)), ender);
+                    /* for now we always disable this optimisation * /
+                    if ( OP(NEXTOPER(NEXTOPER(br))) != NOTHING
+                         || regnext(NEXTOPER(NEXTOPER(br))) != ender)
+                    */
+                        is_nothing= 0;
+               }
+           }
+            if (is_nothing) {
+                br= PL_regkind[OP(ret)] != BRANCH ? regnext(ret) : ret;
+                DEBUG_PARSE_r(if (!SIZE_ONLY) {
+                    SV * const mysv_val1=sv_newmortal();
+                    SV * const mysv_val2=sv_newmortal();
+                    DEBUG_PARSE_MSG("NADA");
+                    regprop(RExC_rx, mysv_val1, ret, NULL);
+                    regprop(RExC_rx, mysv_val2, ender, NULL);
+                    PerlIO_printf(Perl_debug_log, "~ converting ret %s (%"IVdf") to ender %s (%"IVdf") offset %"IVdf"\n",
+                                  SvPV_nolen_const(mysv_val1),
+                                  (IV)REG_NODE_NUM(ret),
+                                  SvPV_nolen_const(mysv_val2),
+                                  (IV)REG_NODE_NUM(ender),
+                                  (IV)(ender - ret)
+                    );
+                });
+                OP(br)= NOTHING;
+                if (OP(ender) == TAIL) {
+                    NEXT_OFF(br)= 0;
+                    RExC_emit= br + 1;
+                } else {
+                    regnode *opt;
+                    for ( opt= br + 1; opt < ender ; opt++ )
+                        OP(opt)= OPTIMIZED;
+                    NEXT_OFF(br)= ender - br;
+                }
+            }
+       }
+    }
+
+    {
+        const char *p;
+        static const char parens[] = "=!<,>";
+
+       if (paren && (p = strchr(parens, paren))) {
+           U8 node = ((p - parens) % 2) ? UNLESSM : IFMATCH;
+           int flag = (p - parens) > 1;
+
+           if (paren == '>')
+               node = SUSPEND, flag = 0;
+           reginsert(pRExC_state, node,ret, depth+1);
+            Set_Node_Cur_Length(ret, parse_start);
+           Set_Node_Offset(ret, parse_start + 1);
+           ret->flags = flag;
+            REGTAIL_STUDY(pRExC_state, ret, reg_node(pRExC_state, TAIL));
+       }
+    }
+
+    /* Check for proper termination. */
+    if (paren) {
+        /* restore original flags, but keep (?p) */
+       RExC_flags = oregflags | (RExC_flags & RXf_PMf_KEEPCOPY);
+       if (RExC_parse >= RExC_end || *nextchar(pRExC_state) != ')') {
+           RExC_parse = oregcomp_parse;
+           vFAIL("Unmatched (");
+       }
+    }
+    else if (!paren && RExC_parse < RExC_end) {
+       if (*RExC_parse == ')') {
+           RExC_parse++;
+           vFAIL("Unmatched )");
+       }
+       else
+           FAIL("Junk on end of regexp");      /* "Can't happen". */
+       assert(0); /* NOTREACHED */
+    }
+
+    if (RExC_in_lookbehind) {
+       RExC_in_lookbehind--;
+    }
+    if (after_freeze > RExC_npar)
+        RExC_npar = after_freeze;
+    return(ret);
+}
+
+/*
+ - regbranch - one alternative of an | operator
+ *
+ * Implements the concatenation operator.
+ *
+ * Returns NULL, setting *flagp to RESTART_UTF8 if the sizing scan needs to be
+ * restarted.
+ */
+STATIC regnode *
+S_regbranch(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, I32 first, U32 depth)
+{
+    dVAR;
+    regnode *ret;
+    regnode *chain = NULL;
+    regnode *latest;
+    I32 flags = 0, c = 0;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGBRANCH;
+
+    DEBUG_PARSE("brnc");
+
+    if (first)
+       ret = NULL;
+    else {
+       if (!SIZE_ONLY && RExC_extralen)
+           ret = reganode(pRExC_state, BRANCHJ,0);
+       else {
+           ret = reg_node(pRExC_state, BRANCH);
+            Set_Node_Length(ret, 1);
+        }
+    }
+
+    if (!first && SIZE_ONLY)
+       RExC_extralen += 1;                     /* BRANCHJ */
+
+    *flagp = WORST;                    /* Tentatively. */
+
+    RExC_parse--;
+    nextchar(pRExC_state);
+    while (RExC_parse < RExC_end && *RExC_parse != '|' && *RExC_parse != ')') {
+       flags &= ~TRYAGAIN;
+        latest = regpiece(pRExC_state, &flags,depth+1);
+       if (latest == NULL) {
+           if (flags & TRYAGAIN)
+               continue;
+            if (flags & RESTART_UTF8) {
+                *flagp = RESTART_UTF8;
+                return NULL;
+            }
+            FAIL2("panic: regpiece returned NULL, flags=%#"UVxf"", (UV) flags);
+       }
+       else if (ret == NULL)
+           ret = latest;
+       *flagp |= flags&(HASWIDTH|POSTPONED);
+       if (chain == NULL)      /* First piece. */
+           *flagp |= flags&SPSTART;
+       else {
+           RExC_naughty++;
+            REGTAIL(pRExC_state, chain, latest);
+       }
+       chain = latest;
+       c++;
+    }
+    if (chain == NULL) {       /* Loop ran zero times. */
+       chain = reg_node(pRExC_state, NOTHING);
+       if (ret == NULL)
+           ret = chain;
+    }
+    if (c == 1) {
+       *flagp |= flags&SIMPLE;
+    }
+
+    return ret;
+}
+
+/*
+ - regpiece - something followed by possible [*+?]
+ *
+ * Note that the branching code sequences used for ? and the general cases
+ * of * and + are somewhat optimized:  they use the same NOTHING node as
+ * both the endmarker for their branch list and the body of the last branch.
+ * It might seem that this node could be dispensed with entirely, but the
+ * endmarker role is not redundant.
+ *
+ * Returns NULL, setting *flagp to TRYAGAIN if regatom() returns NULL with
+ * TRYAGAIN.
+ * Returns NULL, setting *flagp to RESTART_UTF8 if the sizing scan needs to be
+ * restarted.
+ */
+STATIC regnode *
+S_regpiece(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
+{
+    dVAR;
+    regnode *ret;
+    char op;
+    char *next;
+    I32 flags;
+    const char * const origparse = RExC_parse;
+    I32 min;
+    I32 max = REG_INFTY;
+#ifdef RE_TRACK_PATTERN_OFFSETS
+    char *parse_start;
+#endif
+    const char *maxpos = NULL;
+
+    /* Save the original in case we change the emitted regop to a FAIL. */
+    regnode * const orig_emit = RExC_emit;
+
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGPIECE;
+
+    DEBUG_PARSE("piec");
+
+    ret = regatom(pRExC_state, &flags,depth+1);
+    if (ret == NULL) {
+       if (flags & (TRYAGAIN|RESTART_UTF8))
+           *flagp |= flags & (TRYAGAIN|RESTART_UTF8);
+        else
+            FAIL2("panic: regatom returned NULL, flags=%#"UVxf"", (UV) flags);
+       return(NULL);
+    }
+
+    op = *RExC_parse;
+
+    if (op == '{' && regcurly(RExC_parse, FALSE)) {
+       maxpos = NULL;
+#ifdef RE_TRACK_PATTERN_OFFSETS
+        parse_start = RExC_parse; /* MJD */
+#endif
+       next = RExC_parse + 1;
+       while (isDIGIT(*next) || *next == ',') {
+           if (*next == ',') {
+               if (maxpos)
+                   break;
+               else
+                   maxpos = next;
+           }
+           next++;
+       }
+       if (*next == '}') {             /* got one */
+           if (!maxpos)
+               maxpos = next;
+           RExC_parse++;
+           min = atoi(RExC_parse);
+           if (*maxpos == ',')
+               maxpos++;
+           else
+               maxpos = RExC_parse;
+           max = atoi(maxpos);
+           if (!max && *maxpos != '0')
+               max = REG_INFTY;                /* meaning "infinity" */
+           else if (max >= REG_INFTY)
+               vFAIL2("Quantifier in {,} bigger than %d", REG_INFTY - 1);
+           RExC_parse = next;
+           nextchar(pRExC_state);
+            if (max < min) {    /* If can't match, warn and optimize to fail
+                                   unconditionally */
+                if (SIZE_ONLY) {
+                    ckWARNreg(RExC_parse, "Quantifier {n,m} with n > m can't match");
+
+                    /* We can't back off the size because we have to reserve
+                     * enough space for all the things we are about to throw
+                     * away, but we can shrink it by the ammount we are about
+                     * to re-use here */
+                    RExC_size = PREVOPER(RExC_size) - regarglen[(U8)OPFAIL];
+                }
+                else {
+                    RExC_emit = orig_emit;
+                }
+                ret = reg_node(pRExC_state, OPFAIL);
+                return ret;
+            }
+            else if (min == max
+                     && RExC_parse < RExC_end
+                     && (*RExC_parse == '?' || *RExC_parse == '+'))
+            {
+                if (SIZE_ONLY) {
+                    ckWARN2reg(RExC_parse + 1,
+                               "Useless use of greediness modifier '%c'",
+                               *RExC_parse);
+                }
+                /* Absorb the modifier, so later code doesn't see nor use
+                    * it */
+                nextchar(pRExC_state);
+            }
+
+       do_curly:
+           if ((flags&SIMPLE)) {
+               RExC_naughty += 2 + RExC_naughty / 2;
+               reginsert(pRExC_state, CURLY, ret, depth+1);
+                Set_Node_Offset(ret, parse_start+1); /* MJD */
+                Set_Node_Cur_Length(ret, parse_start);
+           }
+           else {
+               regnode * const w = reg_node(pRExC_state, WHILEM);
+
+               w->flags = 0;
+                REGTAIL(pRExC_state, ret, w);
+               if (!SIZE_ONLY && RExC_extralen) {
+                   reginsert(pRExC_state, LONGJMP,ret, depth+1);
+                   reginsert(pRExC_state, NOTHING,ret, depth+1);
+                   NEXT_OFF(ret) = 3;  /* Go over LONGJMP. */
+               }
+               reginsert(pRExC_state, CURLYX,ret, depth+1);
+                                /* MJD hk */
+                Set_Node_Offset(ret, parse_start+1);
+                Set_Node_Length(ret,
+                                op == '{' ? (RExC_parse - parse_start) : 1);
+
+               if (!SIZE_ONLY && RExC_extralen)
+                   NEXT_OFF(ret) = 3;  /* Go over NOTHING to LONGJMP. */
+                REGTAIL(pRExC_state, ret, reg_node(pRExC_state, NOTHING));
+               if (SIZE_ONLY)
+                   RExC_whilem_seen++, RExC_extralen += 3;
+               RExC_naughty += 4 + RExC_naughty;       /* compound interest */
+           }
+           ret->flags = 0;
+
+           if (min > 0)
+               *flagp = WORST;
+           if (max > 0)
+               *flagp |= HASWIDTH;
+           if (!SIZE_ONLY) {
+               ARG1_SET(ret, (U16)min);
+               ARG2_SET(ret, (U16)max);
+           }
+            if (max == REG_INFTY)
+                RExC_seen |= REG_UNBOUNDED_QUANTIFIER_SEEN;
+
+           goto nest_check;
+       }
+    }
+
+    if (!ISMULT1(op)) {
+       *flagp = flags;
+       return(ret);
+    }
+
+#if 0                          /* Now runtime fix should be reliable. */
+
+    /* if this is reinstated, don't forget to put this back into perldiag:
+
+           =item Regexp *+ operand could be empty at {#} in regex m/%s/
+
+          (F) The part of the regexp subject to either the * or + quantifier
+           could match an empty string. The {#} shows in the regular
+           expression about where the problem was discovered.
+
+    */
+
+    if (!(flags&HASWIDTH) && op != '?')
+      vFAIL("Regexp *+ operand could be empty");
+#endif
+
+#ifdef RE_TRACK_PATTERN_OFFSETS
+    parse_start = RExC_parse;
+#endif
+    nextchar(pRExC_state);
+
+    *flagp = (op != '+') ? (WORST|SPSTART|HASWIDTH) : (WORST|HASWIDTH);
+
+    if (op == '*' && (flags&SIMPLE)) {
+       reginsert(pRExC_state, STAR, ret, depth+1);
+       ret->flags = 0;
+       RExC_naughty += 4;
+        RExC_seen |= REG_UNBOUNDED_QUANTIFIER_SEEN;
+    }
+    else if (op == '*') {
+       min = 0;
+       goto do_curly;
+    }
+    else if (op == '+' && (flags&SIMPLE)) {
+       reginsert(pRExC_state, PLUS, ret, depth+1);
+       ret->flags = 0;
+       RExC_naughty += 3;
+        RExC_seen |= REG_UNBOUNDED_QUANTIFIER_SEEN;
+    }
+    else if (op == '+') {
+       min = 1;
+       goto do_curly;
+    }
+    else if (op == '?') {
+       min = 0; max = 1;
+       goto do_curly;
+    }
+  nest_check:
+    if (!SIZE_ONLY && !(flags&(HASWIDTH|POSTPONED)) && max > REG_INFTY/3) {
+       SAVEFREESV(RExC_rx_sv); /* in case of fatal warnings */
+       ckWARN2reg(RExC_parse,
+                  "%"UTF8f" matches null string many times",
+                  UTF8fARG(UTF, (RExC_parse >= origparse
+                                 ? RExC_parse - origparse
+                                 : 0),
+                  origparse));
+       (void)ReREFCNT_inc(RExC_rx_sv);
+    }
+
+    if (RExC_parse < RExC_end && *RExC_parse == '?') {
+       nextchar(pRExC_state);
+       reginsert(pRExC_state, MINMOD, ret, depth+1);
+        REGTAIL(pRExC_state, ret, ret + NODE_STEP_REGNODE);
+    }
+    else
+    if (RExC_parse < RExC_end && *RExC_parse == '+') {
+        regnode *ender;
+        nextchar(pRExC_state);
+        ender = reg_node(pRExC_state, SUCCEED);
+        REGTAIL(pRExC_state, ret, ender);
+        reginsert(pRExC_state, SUSPEND, ret, depth+1);
+        ret->flags = 0;
+        ender = reg_node(pRExC_state, TAIL);
+        REGTAIL(pRExC_state, ret, ender);
+    }
+
+    if (RExC_parse < RExC_end && ISMULT2(RExC_parse)) {
+       RExC_parse++;
+       vFAIL("Nested quantifiers");
+    }
+
+    return(ret);
+}
+
+STATIC bool
+S_grok_bslash_N(pTHX_ RExC_state_t *pRExC_state, regnode** node_p,
+                      UV *valuep, I32 *flagp, U32 depth, bool in_char_class,
+                      const bool strict   /* Apply stricter parsing rules? */
+    )
+{
+
+ /* This is expected to be called by a parser routine that has recognized '\N'
+   and needs to handle the rest. RExC_parse is expected to point at the first
+   char following the N at the time of the call.  On successful return,
+   RExC_parse has been updated to point to just after the sequence identified
+   by this routine, and <*flagp> has been updated.
+
+   The \N may be inside (indicated by the boolean <in_char_class>) or outside a
+   character class.
+
+   \N may begin either a named sequence, or if outside a character class, mean
+   to match a non-newline.  For non single-quoted regexes, the tokenizer has
+   attempted to decide which, and in the case of a named sequence, converted it
+   into one of the forms: \N{} (if the sequence is null), or \N{U+c1.c2...},
+   where c1... are the characters in the sequence.  For single-quoted regexes,
+   the tokenizer passes the \N sequence through unchanged; this code will not
+   attempt to determine this nor expand those, instead raising a syntax error.
+   The net effect is that if the beginning of the passed-in pattern isn't '{U+'
+   or there is no '}', it signals that this \N occurrence means to match a
+   non-newline.
+
+   Only the \N{U+...} form should occur in a character class, for the same
+   reason that '.' inside a character class means to just match a period: it
+   just doesn't make sense.
+
+   The function raises an error (via vFAIL), and doesn't return for various
+   syntax errors.  Otherwise it returns TRUE and sets <node_p> or <valuep> on
+   success; it returns FALSE otherwise. Returns FALSE, setting *flagp to
+   RESTART_UTF8 if the sizing scan needs to be restarted. Such a restart is
+   only possible if node_p is non-NULL.
+
+
+   If <valuep> is non-null, it means the caller can accept an input sequence
+   consisting of a just a single code point; <*valuep> is set to that value
+   if the input is such.
+
+   If <node_p> is non-null it signifies that the caller can accept any other
+   legal sequence (i.e., one that isn't just a single code point).  <*node_p>
+   is set as follows:
+    1) \N means not-a-NL: points to a newly created REG_ANY node;
+    2) \N{}:              points to a new NOTHING node;
+    3) otherwise:         points to a new EXACT node containing the resolved
+                          string.
+   Note that FALSE is returned for single code point sequences if <valuep> is
+   null.
+ */
+
+    char * endbrace;    /* '}' following the name */
+    char* p;
+    char *endchar;     /* Points to '.' or '}' ending cur char in the input
+                           stream */
+    bool has_multiple_chars; /* true if the input stream contains a sequence of
+                                more than one character */
+
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_GROK_BSLASH_N;
+
+    GET_RE_DEBUG_FLAGS;
+
+    assert(cBOOL(node_p) ^ cBOOL(valuep));  /* Exactly one should be set */
+
+    /* The [^\n] meaning of \N ignores spaces and comments under the /x
+     * modifier.  The other meaning does not, so use a temporary until we find
+     * out which we are being called with */
+    p = (RExC_flags & RXf_PMf_EXTENDED)
+       ? regwhite( pRExC_state, RExC_parse )
+       : RExC_parse;
+
+    /* Disambiguate between \N meaning a named character versus \N meaning
+     * [^\n].  The former is assumed when it can't be the latter. */
+    if (*p != '{' || regcurly(p, FALSE)) {
+       RExC_parse = p;
+       if (! node_p) {
+           /* no bare \N allowed in a charclass */
+            if (in_char_class) {
+                vFAIL("\\N in a character class must be a named character: \\N{...}");
+            }
+            return FALSE;
+        }
+        RExC_parse--;   /* Need to back off so nextchar() doesn't skip the
+                           current char */
+       nextchar(pRExC_state);
+       *node_p = reg_node(pRExC_state, REG_ANY);
+       *flagp |= HASWIDTH|SIMPLE;
+       RExC_naughty++;
+        Set_Node_Length(*node_p, 1); /* MJD */
+       return TRUE;
+    }
+
+    /* Here, we have decided it should be a named character or sequence */
+
+    /* The test above made sure that the next real character is a '{', but
+     * under the /x modifier, it could be separated by space (or a comment and
+     * \n) and this is not allowed (for consistency with \x{...} and the
+     * tokenizer handling of \N{NAME}). */
+    if (*RExC_parse != '{') {
+       vFAIL("Missing braces on \\N{}");
+    }
+
+    RExC_parse++;      /* Skip past the '{' */
+
+    if (! (endbrace = strchr(RExC_parse, '}')) /* no trailing brace */
+       || ! (endbrace == RExC_parse            /* nothing between the {} */
+              || (endbrace - RExC_parse >= 2   /* U+ (bad hex is checked below
+                                                 */
+                  && strnEQ(RExC_parse, "U+", 2)))) /* for a better error msg)
+                                                     */
+    {
+       if (endbrace) RExC_parse = endbrace;    /* position msg's '<--HERE' */
+       vFAIL("\\N{NAME} must be resolved by the lexer");
+    }
+
+    if (endbrace == RExC_parse) {   /* empty: \N{} */
+        bool ret = TRUE;
+       if (node_p) {
+           *node_p = reg_node(pRExC_state,NOTHING);
+       }
+        else if (in_char_class) {
+            if (SIZE_ONLY && in_char_class) {
+                if (strict) {
+                    RExC_parse++;   /* Position after the "}" */
+                    vFAIL("Zero length \\N{}");
+                }
+                else {
+                    ckWARNreg(RExC_parse,
+                              "Ignoring zero length \\N{} in character class");
+                }
+            }
+            ret = FALSE;
+       }
+        else {
+            return FALSE;
+        }
+        nextchar(pRExC_state);
+        return ret;
+    }
+
+    RExC_uni_semantics = 1; /* Unicode named chars imply Unicode semantics */
+    RExC_parse += 2;   /* Skip past the 'U+' */
+
+    endchar = RExC_parse + strcspn(RExC_parse, ".}");
+
+    /* Code points are separated by dots.  If none, there is only one code
+     * point, and is terminated by the brace */
+    has_multiple_chars = (endchar < endbrace);
+
+    if (valuep && (! has_multiple_chars || in_char_class)) {
+       /* We only pay attention to the first char of
+        multichar strings being returned in char classes. I kinda wonder
+       if this makes sense as it does change the behaviour
+       from earlier versions, OTOH that behaviour was broken
+       as well. XXX Solution is to recharacterize as
+       [rest-of-class]|multi1|multi2... */
+
+       STRLEN length_of_hex = (STRLEN)(endchar - RExC_parse);
+       I32 grok_hex_flags = PERL_SCAN_ALLOW_UNDERSCORES
+           | PERL_SCAN_DISALLOW_PREFIX
+           | (SIZE_ONLY ? PERL_SCAN_SILENT_ILLDIGIT : 0);
+
+       *valuep = grok_hex(RExC_parse, &length_of_hex, &grok_hex_flags, NULL);
+
+       /* The tokenizer should have guaranteed validity, but it's possible to
+        * bypass it by using single quoting, so check */
+       if (length_of_hex == 0
+           || length_of_hex != (STRLEN)(endchar - RExC_parse) )
+       {
+           RExC_parse += length_of_hex;        /* Includes all the valid */
+           RExC_parse += (RExC_orig_utf8)      /* point to after 1st invalid */
+                           ? UTF8SKIP(RExC_parse)
+                           : 1;
+           /* Guard against malformed utf8 */
+           if (RExC_parse >= endchar) {
+                RExC_parse = endchar;
+            }
+           vFAIL("Invalid hexadecimal number in \\N{U+...}");
+       }
+
+        if (in_char_class && has_multiple_chars) {
+            if (strict) {
+                RExC_parse = endbrace;
+                vFAIL("\\N{} in character class restricted to one character");
+            }
+            else {
+                ckWARNreg(endchar, "Using just the first character returned by \\N{} in character class");
+            }
+        }
+
+        RExC_parse = endbrace + 1;
+    }
+    else if (! node_p || ! has_multiple_chars) {
+
+        /* Here, the input is legal, but not according to the caller's
+         * options.  We fail without advancing the parse, so that the
+         * caller can try again */
+        RExC_parse = p;
+        return FALSE;
+    }
+    else {
+
+       /* What is done here is to convert this to a sub-pattern of the form
+        * (?:\x{char1}\x{char2}...)
+        * and then call reg recursively.  That way, it retains its atomicness,
+        * while not having to worry about special handling that some code
+        * points may have.  toke.c has converted the original Unicode values
+        * to native, so that we can just pass on the hex values unchanged.  We
+        * do have to set a flag to keep recoding from happening in the
+        * recursion */
+
+       SV * substitute_parse = newSVpvn_flags("?:", 2, SVf_UTF8|SVs_TEMP);
+       STRLEN len;
+       char *orig_end = RExC_end;
+        I32 flags;
+
+       while (RExC_parse < endbrace) {
+
+           /* Convert to notation the rest of the code understands */
+           sv_catpv(substitute_parse, "\\x{");
+           sv_catpvn(substitute_parse, RExC_parse, endchar - RExC_parse);
+           sv_catpv(substitute_parse, "}");
+
+           /* Point to the beginning of the next character in the sequence. */
+           RExC_parse = endchar + 1;
+           endchar = RExC_parse + strcspn(RExC_parse, ".}");
+       }
+       sv_catpv(substitute_parse, ")");
+
+       RExC_parse = SvPV(substitute_parse, len);
+
+       /* Don't allow empty number */
+       if (len < 8) {
+           vFAIL("Invalid hexadecimal number in \\N{U+...}");
+       }
+       RExC_end = RExC_parse + len;
+
+       /* The values are Unicode, and therefore not subject to recoding */
+       RExC_override_recoding = 1;
+
+       if (!(*node_p = reg(pRExC_state, 1, &flags, depth+1))) {
+            if (flags & RESTART_UTF8) {
+                *flagp = RESTART_UTF8;
+                return FALSE;
+            }
+            FAIL2("panic: reg returned NULL to grok_bslash_N, flags=%#"UVxf"",
+                  (UV) flags);
+        }
+       *flagp |= flags&(HASWIDTH|SPSTART|SIMPLE|POSTPONED);
+
+       RExC_parse = endbrace;
+       RExC_end = orig_end;
+       RExC_override_recoding = 0;
+
+        nextchar(pRExC_state);
+    }
+
+    return TRUE;
+}
+
+
+/*
+ * reg_recode
+ *
+ * It returns the code point in utf8 for the value in *encp.
+ *    value: a code value in the source encoding
+ *    encp:  a pointer to an Encode object
+ *
+ * If the result from Encode is not a single character,
+ * it returns U+FFFD (Replacement character) and sets *encp to NULL.
+ */
+STATIC UV
+S_reg_recode(pTHX_ const char value, SV **encp)
+{
+    STRLEN numlen = 1;
+    SV * const sv = newSVpvn_flags(&value, numlen, SVs_TEMP);
+    const char * const s = *encp ? sv_recode_to_utf8(sv, *encp) : SvPVX(sv);
+    const STRLEN newlen = SvCUR(sv);
+    UV uv = UNICODE_REPLACEMENT;
+
+    PERL_ARGS_ASSERT_REG_RECODE;
+
+    if (newlen)
+       uv = SvUTF8(sv)
+            ? utf8n_to_uvchr((U8*)s, newlen, &numlen, UTF8_ALLOW_DEFAULT)
+            : *(U8*)s;
+
+    if (!newlen || numlen != newlen) {
+       uv = UNICODE_REPLACEMENT;
+       *encp = NULL;
+    }
+    return uv;
+}
+
+PERL_STATIC_INLINE U8
+S_compute_EXACTish(pTHX_ RExC_state_t *pRExC_state)
+{
+    U8 op;
+
+    PERL_ARGS_ASSERT_COMPUTE_EXACTISH;
+
+    if (! FOLD) {
+        return EXACT;
+    }
+
+    op = get_regex_charset(RExC_flags);
+    if (op >= REGEX_ASCII_RESTRICTED_CHARSET) {
+        op--; /* /a is same as /u, and map /aa's offset to what /a's would have
+                 been, so there is no hole */
+    }
+
+    return op + EXACTF;
+}
+
+PERL_STATIC_INLINE void
+S_alloc_maybe_populate_EXACT(pTHX_ RExC_state_t *pRExC_state,
+                         regnode *node, I32* flagp, STRLEN len, UV code_point,
+                         bool downgradable)
+{
+    /* This knows the details about sizing an EXACTish node, setting flags for
+     * it (by setting <*flagp>, and potentially populating it with a single
+     * character.
+     *
+     * If <len> (the length in bytes) is non-zero, this function assumes that
+     * the node has already been populated, and just does the sizing.  In this
+     * case <code_point> should be the final code point that has already been
+     * placed into the node.  This value will be ignored except that under some
+     * circumstances <*flagp> is set based on it.
+     *
+     * If <len> is zero, the function assumes that the node is to contain only
+     * the single character given by <code_point> and calculates what <len>
+     * should be.  In pass 1, it sizes the node appropriately.  In pass 2, it
+     * additionally will populate the node's STRING with <code_point> or its
+     * fold if folding.
+     *
+     * In both cases <*flagp> is appropriately set
+     *
+     * It knows that under FOLD, the Latin Sharp S and UTF characters above
+     * 255, must be folded (the former only when the rules indicate it can
+     * match 'ss')
+     *
+     * When it does the populating, it looks at the flag 'downgradable'.  If
+     * true with a node that folds, it checks if the single code point
+     * participates in a fold, and if not downgrades the node to an EXACT.
+     * This helps the optimizer */
+
+    bool len_passed_in = cBOOL(len != 0);
+    U8 character[UTF8_MAXBYTES_CASE+1];
+
+    PERL_ARGS_ASSERT_ALLOC_MAYBE_POPULATE_EXACT;
+
+    /* Don't bother to check for downgrading in PASS1, as it doesn't make any
+     * sizing difference, and is extra work that is thrown away */
+    if (downgradable && ! PASS2) {
+        downgradable = FALSE;
+    }
+
+    if (! len_passed_in) {
+        if (UTF) {
+            if (UNI_IS_INVARIANT(code_point)) {
+                if (LOC || ! FOLD) {    /* /l defers folding until runtime */
+                    *character = (U8) code_point;
+                }
+                else { /* Here is /i and not /l (toFOLD() is defined on just
+                          ASCII, which isn't the same thing as INVARIANT on
+                          EBCDIC, but it works there, as the extra invariants
+                          fold to themselves) */
+                    *character = toFOLD((U8) code_point);
+
+                    /* We can downgrade to an EXACT node if this character
+                     * isn't a folding one.  Note that this assumes that
+                     * nothing above Latin1 folds to some other invariant than
+                     * one of these alphabetics; otherwise we would also have
+                     * to check:
+                     *  && (! HAS_NONLATIN1_FOLD_CLOSURE(code_point)
+                     *      || ASCII_FOLD_RESTRICTED))
+                     */
+                    if (downgradable && PL_fold[code_point] == code_point) {
+                        OP(node) = EXACT;
+                    }
+                }
+                len = 1;
+            }
+            else if (FOLD && (! LOC
+                              || ! is_PROBLEMATIC_LOCALE_FOLD_cp(code_point)))
+            {   /* Folding, and ok to do so now */
+                UV folded = _to_uni_fold_flags(
+                                   code_point,
+                                   character,
+                                   &len,
+                                   FOLD_FLAGS_FULL | ((ASCII_FOLD_RESTRICTED)
+                                                      ? FOLD_FLAGS_NOMIX_ASCII
+                                                      : 0));
+                if (downgradable
+                    && folded == code_point
+                    && ! _invlist_contains_cp(PL_utf8_foldable, code_point))
+                {
+                    OP(node) = EXACT;
+                }
+            }
+            else if (code_point <= MAX_UTF8_TWO_BYTE) {
+
+                /* Not folding this cp, and can output it directly */
+                *character = UTF8_TWO_BYTE_HI(code_point);
+                *(character + 1) = UTF8_TWO_BYTE_LO(code_point);
+                len = 2;
+            }
+            else {
+                uvchr_to_utf8( character, code_point);
+                len = UTF8SKIP(character);
+            }
+        } /* Else pattern isn't UTF8.  */
+        else if (! FOLD) {
+            *character = (U8) code_point;
+            len = 1;
+        } /* Else is folded non-UTF8 */
+        else if (LIKELY(code_point != LATIN_SMALL_LETTER_SHARP_S)) {
+
+            /* We don't fold any non-UTF8 except possibly the Sharp s  (see
+             * comments at join_exact()); */
+            *character = (U8) code_point;
+            len = 1;
+
+            /* Can turn into an EXACT node if we know the fold at compile time,
+             * and it folds to itself and doesn't particpate in other folds */
+            if (downgradable
+                && ! LOC
+                && PL_fold_latin1[code_point] == code_point
+                && (! HAS_NONLATIN1_FOLD_CLOSURE(code_point)
+                    || (isASCII(code_point) && ASCII_FOLD_RESTRICTED)))
+            {
+                OP(node) = EXACT;
+            }
+        } /* else is Sharp s.  May need to fold it */
+        else if (AT_LEAST_UNI_SEMANTICS && ! ASCII_FOLD_RESTRICTED) {
+            *character = 's';
+            *(character + 1) = 's';
+            len = 2;
+        }
+        else {
+            *character = LATIN_SMALL_LETTER_SHARP_S;
+            len = 1;
+        }
+    }
+
+    if (SIZE_ONLY) {
+        RExC_size += STR_SZ(len);
+    }
+    else {
+        RExC_emit += STR_SZ(len);
+        STR_LEN(node) = len;
+        if (! len_passed_in) {
+            Copy((char *) character, STRING(node), len, char);
+        }
+    }
+
+    *flagp |= HASWIDTH;
+
+    /* A single character node is SIMPLE, except for the special-cased SHARP S
+     * under /di. */
+    if ((len == 1 || (UTF && len == UNISKIP(code_point)))
+        && (code_point != LATIN_SMALL_LETTER_SHARP_S
+            || ! FOLD || ! DEPENDS_SEMANTICS))
+    {
+        *flagp |= SIMPLE;
+    }
+
+    /* The OP may not be well defined in PASS1 */
+    if (PASS2 && OP(node) == EXACTFL) {
+        RExC_contains_locale = 1;
+    }
+}
+
+
+/* return atoi(p), unless it's too big to sensibly be a backref,
+ * in which case return I32_MAX (rather than possibly 32-bit wrapping) */
+
+static I32
+S_backref_value(char *p)
+{
+    char *q = p;
+
+    for (;isDIGIT(*q); q++); /* calculate length of num */
+    if (q - p == 0 || q - p > 9)
+        return I32_MAX;
+    return atoi(p);
+}
+
+
+/*
+ - regatom - the lowest level
+
+   Try to identify anything special at the start of the pattern. If there
+   is, then handle it as required. This may involve generating a single regop,
+   such as for an assertion; or it may involve recursing, such as to
+   handle a () structure.
+
+   If the string doesn't start with something special then we gobble up
+   as much literal text as we can.
+
+   Once we have been able to handle whatever type of thing started the
+   sequence, we return.
+
+   Note: we have to be careful with escapes, as they can be both literal
+   and special, and in the case of \10 and friends, context determines which.
+
+   A summary of the code structure is:
+
+   switch (first_byte) {
+       cases for each special:
+           handle this special;
+           break;
+       case '\\':
+           switch (2nd byte) {
+               cases for each unambiguous special:
+                   handle this special;
+                   break;
+               cases for each ambigous special/literal:
+                   disambiguate;
+                   if (special)  handle here
+                   else goto defchar;
+               default: // unambiguously literal:
+                   goto defchar;
+           }
+       default:  // is a literal char
+           // FALL THROUGH
+       defchar:
+           create EXACTish node for literal;
+           while (more input and node isn't full) {
+               switch (input_byte) {
+                  cases for each special;
+                       make sure parse pointer is set so that the next call to
+                           regatom will see this special first
+                       goto loopdone; // EXACTish node terminated by prev. char
+                  default:
+                      append char to EXACTISH node;
+               }
+               get next input byte;
+           }
+        loopdone:
+   }
+   return the generated node;
+
+   Specifically there are two separate switches for handling
+   escape sequences, with the one for handling literal escapes requiring
+   a dummy entry for all of the special escapes that are actually handled
+   by the other.
+
+   Returns NULL, setting *flagp to TRYAGAIN if reg() returns NULL with
+   TRYAGAIN.
+   Returns NULL, setting *flagp to RESTART_UTF8 if the sizing scan needs to be
+   restarted.
+   Otherwise does not return NULL.
+*/
+
+STATIC regnode *
+S_regatom(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth)
+{
+    dVAR;
+    regnode *ret = NULL;
+    I32 flags = 0;
+    char *parse_start = RExC_parse;
+    U8 op;
+    int invert = 0;
+
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    *flagp = WORST;            /* Tentatively. */
+
+    DEBUG_PARSE("atom");
+
+    PERL_ARGS_ASSERT_REGATOM;
+
+tryagain:
+    switch ((U8)*RExC_parse) {
+    case '^':
+       RExC_seen_zerolen++;
+       nextchar(pRExC_state);
+       if (RExC_flags & RXf_PMf_MULTILINE)
+           ret = reg_node(pRExC_state, MBOL);
+       else if (RExC_flags & RXf_PMf_SINGLELINE)
+           ret = reg_node(pRExC_state, SBOL);
+       else
+           ret = reg_node(pRExC_state, BOL);
+        Set_Node_Length(ret, 1); /* MJD */
+       break;
+    case '$':
+       nextchar(pRExC_state);
+       if (*RExC_parse)
+           RExC_seen_zerolen++;
+       if (RExC_flags & RXf_PMf_MULTILINE)
+           ret = reg_node(pRExC_state, MEOL);
+       else if (RExC_flags & RXf_PMf_SINGLELINE)
+           ret = reg_node(pRExC_state, SEOL);
+       else
+           ret = reg_node(pRExC_state, EOL);
+        Set_Node_Length(ret, 1); /* MJD */
+       break;
+    case '.':
+       nextchar(pRExC_state);
+       if (RExC_flags & RXf_PMf_SINGLELINE)
+           ret = reg_node(pRExC_state, SANY);
+       else
+           ret = reg_node(pRExC_state, REG_ANY);
+       *flagp |= HASWIDTH|SIMPLE;
+       RExC_naughty++;
+        Set_Node_Length(ret, 1); /* MJD */
+       break;
+    case '[':
+    {
+       char * const oregcomp_parse = ++RExC_parse;
+        ret = regclass(pRExC_state, flagp,depth+1,
+                       FALSE, /* means parse the whole char class */
+                       TRUE, /* allow multi-char folds */
+                       FALSE, /* don't silence non-portable warnings. */
+                       NULL);
+       if (*RExC_parse != ']') {
+           RExC_parse = oregcomp_parse;
+           vFAIL("Unmatched [");
+       }
+        if (ret == NULL) {
+            if (*flagp & RESTART_UTF8)
+                return NULL;
+            FAIL2("panic: regclass returned NULL to regatom, flags=%#"UVxf"",
+                  (UV) *flagp);
+        }
+       nextchar(pRExC_state);
+        Set_Node_Length(ret, RExC_parse - oregcomp_parse + 1); /* MJD */
+       break;
+    }
+    case '(':
+       nextchar(pRExC_state);
+        ret = reg(pRExC_state, 2, &flags,depth+1);
+       if (ret == NULL) {
+               if (flags & TRYAGAIN) {
+                   if (RExC_parse == RExC_end) {
+                        /* Make parent create an empty node if needed. */
+                       *flagp |= TRYAGAIN;
+                       return(NULL);
+                   }
+                   goto tryagain;
+               }
+                if (flags & RESTART_UTF8) {
+                    *flagp = RESTART_UTF8;
+                    return NULL;
+                }
+                FAIL2("panic: reg returned NULL to regatom, flags=%#"UVxf"",
+                                                                 (UV) flags);
+       }
+       *flagp |= flags&(HASWIDTH|SPSTART|SIMPLE|POSTPONED);
+       break;
+    case '|':
+    case ')':
+       if (flags & TRYAGAIN) {
+           *flagp |= TRYAGAIN;
+           return NULL;
+       }
+       vFAIL("Internal urp");
+                               /* Supposed to be caught earlier. */
+       break;
+    case '{':
+       if (!regcurly(RExC_parse, FALSE)) {
+           RExC_parse++;
+           goto defchar;
+       }
+       /* FALL THROUGH */
+    case '?':
+    case '+':
+    case '*':
+       RExC_parse++;
+       vFAIL("Quantifier follows nothing");
+       break;
+    case '\\':
+       /* Special Escapes
+
+          This switch handles escape sequences that resolve to some kind
+          of special regop and not to literal text. Escape sequnces that
+          resolve to literal text are handled below in the switch marked
+          "Literal Escapes".
+
+          Every entry in this switch *must* have a corresponding entry
+          in the literal escape switch. However, the opposite is not
+          required, as the default for this switch is to jump to the
+          literal text handling code.
+       */
+       switch ((U8)*++RExC_parse) {
+            U8 arg;
+       /* Special Escapes */
+       case 'A':
+           RExC_seen_zerolen++;
+           ret = reg_node(pRExC_state, SBOL);
+           *flagp |= SIMPLE;
+           goto finish_meta_pat;
+       case 'G':
+           ret = reg_node(pRExC_state, GPOS);
+            RExC_seen |= REG_GPOS_SEEN;
+           *flagp |= SIMPLE;
+           goto finish_meta_pat;
+       case 'K':
+           RExC_seen_zerolen++;
+           ret = reg_node(pRExC_state, KEEPS);
+           *flagp |= SIMPLE;
+           /* XXX:dmq : disabling in-place substitution seems to
+            * be necessary here to avoid cases of memory corruption, as
+            * with: C<$_="x" x 80; s/x\K/y/> -- rgs
+            */
+            RExC_seen |= REG_LOOKBEHIND_SEEN;
+           goto finish_meta_pat;
+       case 'Z':
+           ret = reg_node(pRExC_state, SEOL);
+           *flagp |= SIMPLE;
+           RExC_seen_zerolen++;                /* Do not optimize RE away */
+           goto finish_meta_pat;
+       case 'z':
+           ret = reg_node(pRExC_state, EOS);
+           *flagp |= SIMPLE;
+           RExC_seen_zerolen++;                /* Do not optimize RE away */
+           goto finish_meta_pat;
+       case 'C':
+           ret = reg_node(pRExC_state, CANY);
+            RExC_seen |= REG_CANY_SEEN;
+           *flagp |= HASWIDTH|SIMPLE;
+           goto finish_meta_pat;
+       case 'X':
+           ret = reg_node(pRExC_state, CLUMP);
+           *flagp |= HASWIDTH;
+           goto finish_meta_pat;
+
+       case 'W':
+            invert = 1;
+            /* FALLTHROUGH */
+       case 'w':
+            arg = ANYOF_WORDCHAR;
+            goto join_posix;
+
+       case 'b':
+           RExC_seen_zerolen++;
+            RExC_seen |= REG_LOOKBEHIND_SEEN;
+           op = BOUND + get_regex_charset(RExC_flags);
+            if (op > BOUNDA) {  /* /aa is same as /a */
+                op = BOUNDA;
+            }
+            else if (op == BOUNDL) {
+                RExC_contains_locale = 1;
+            }
+           ret = reg_node(pRExC_state, op);
+           FLAGS(ret) = get_regex_charset(RExC_flags);
+           *flagp |= SIMPLE;
+           if (! SIZE_ONLY && (U8) *(RExC_parse + 1) == '{') {
+                /* diag_listed_as: Use "%s" instead of "%s" */
+               vFAIL("Use \"\\b\\{\" instead of \"\\b{\"");
+           }
+           goto finish_meta_pat;
+       case 'B':
+           RExC_seen_zerolen++;
+            RExC_seen |= REG_LOOKBEHIND_SEEN;
+           op = NBOUND + get_regex_charset(RExC_flags);
+            if (op > NBOUNDA) { /* /aa is same as /a */
+                op = NBOUNDA;
+            }
+            else if (op == NBOUNDL) {
+                RExC_contains_locale = 1;
+            }
+           ret = reg_node(pRExC_state, op);
+           FLAGS(ret) = get_regex_charset(RExC_flags);
+           *flagp |= SIMPLE;
+           if (! SIZE_ONLY && (U8) *(RExC_parse + 1) == '{') {
+                /* diag_listed_as: Use "%s" instead of "%s" */
+               vFAIL("Use \"\\B\\{\" instead of \"\\B{\"");
+           }
+           goto finish_meta_pat;
+
+       case 'D':
+            invert = 1;
+            /* FALLTHROUGH */
+       case 'd':
+            arg = ANYOF_DIGIT;
+            goto join_posix;
+
+       case 'R':
+           ret = reg_node(pRExC_state, LNBREAK);
+           *flagp |= HASWIDTH|SIMPLE;
+           goto finish_meta_pat;
+
+       case 'H':
+            invert = 1;
+            /* FALLTHROUGH */
+       case 'h':
+           arg = ANYOF_BLANK;
+            op = POSIXU;
+            goto join_posix_op_known;
+
+       case 'V':
+            invert = 1;
+            /* FALLTHROUGH */
+       case 'v':
+           arg = ANYOF_VERTWS;
+            op = POSIXU;
+            goto join_posix_op_known;
+
+       case 'S':
+            invert = 1;
+            /* FALLTHROUGH */
+       case 's':
+            arg = ANYOF_SPACE;
+
+        join_posix:
+
+           op = POSIXD + get_regex_charset(RExC_flags);
+            if (op > POSIXA) {  /* /aa is same as /a */
+                op = POSIXA;
+            }
+            else if (op == POSIXL) {
+                RExC_contains_locale = 1;
+            }
+
+        join_posix_op_known:
+
+            if (invert) {
+                op += NPOSIXD - POSIXD;
+            }
+
+           ret = reg_node(pRExC_state, op);
+            if (! SIZE_ONLY) {
+                FLAGS(ret) = namedclass_to_classnum(arg);
+            }
+
+           *flagp |= HASWIDTH|SIMPLE;
+            /* FALL THROUGH */
+
+         finish_meta_pat:
+           nextchar(pRExC_state);
+            Set_Node_Length(ret, 2); /* MJD */
+           break;
+       case 'p':
+       case 'P':
+           {
+#ifdef DEBUGGING
+               char* parse_start = RExC_parse - 2;
+#endif
+
+               RExC_parse--;
+
+                ret = regclass(pRExC_state, flagp,depth+1,
+                               TRUE, /* means just parse this element */
+                               FALSE, /* don't allow multi-char folds */
+                               FALSE, /* don't silence non-portable warnings.
+                                         It would be a bug if these returned
+                                         non-portables */
+                               NULL);
+                /* regclass() can only return RESTART_UTF8 if multi-char folds
+                   are allowed.  */
+                if (!ret)
+                    FAIL2("panic: regclass returned NULL to regatom, flags=%#"UVxf"",
+                          (UV) *flagp);
+
+               RExC_parse--;
+
+               Set_Node_Offset(ret, parse_start + 2);
+                Set_Node_Cur_Length(ret, parse_start);
+               nextchar(pRExC_state);
+           }
+           break;
+        case 'N':
+            /* Handle \N and \N{NAME} with multiple code points here and not
+             * below because it can be multicharacter. join_exact() will join
+             * them up later on.  Also this makes sure that things like
+             * /\N{BLAH}+/ and \N{BLAH} being multi char Just Happen. dmq.
+             * The options to the grok function call causes it to fail if the
+             * sequence is just a single code point.  We then go treat it as
+             * just another character in the current EXACT node, and hence it
+             * gets uniform treatment with all the other characters.  The
+             * special treatment for quantifiers is not needed for such single
+             * character sequences */
+            ++RExC_parse;
+            if (! grok_bslash_N(pRExC_state, &ret, NULL, flagp, depth, FALSE,
+                                FALSE /* not strict */ )) {
+                if (*flagp & RESTART_UTF8)
+                    return NULL;
+                RExC_parse--;
+                goto defchar;
+            }
+            break;
+       case 'k':    /* Handle \k<NAME> and \k'NAME' */
+       parse_named_seq:
+        {
+            char ch= RExC_parse[1];
+           if (ch != '<' && ch != '\'' && ch != '{') {
+               RExC_parse++;
+               /* diag_listed_as: Sequence \%s... not terminated in regex; marked by <-- HERE in m/%s/ */
+               vFAIL2("Sequence %.2s... not terminated",parse_start);
+           } else {
+               /* this pretty much dupes the code for (?P=...) in reg(), if
+                   you change this make sure you change that */
+               char* name_start = (RExC_parse += 2);
+               U32 num = 0;
+                SV *sv_dat = reg_scan_name(pRExC_state,
+                    SIZE_ONLY ? REG_RSN_RETURN_NULL : REG_RSN_RETURN_DATA);
+                ch= (ch == '<') ? '>' : (ch == '{') ? '}' : '\'';
+                if (RExC_parse == name_start || *RExC_parse != ch)
+                    /* diag_listed_as: Sequence \%s... not terminated in regex; marked by <-- HERE in m/%s/ */
+                    vFAIL2("Sequence %.3s... not terminated",parse_start);
+
+                if (!SIZE_ONLY) {
+                    num = add_data( pRExC_state, STR_WITH_LEN("S"));
+                    RExC_rxi->data->data[num]=(void*)sv_dat;
+                    SvREFCNT_inc_simple_void(sv_dat);
+                }
+
+                RExC_sawback = 1;
+                ret = reganode(pRExC_state,
+                               ((! FOLD)
+                                 ? NREF
+                                : (ASCII_FOLD_RESTRICTED)
+                                  ? NREFFA
+                                   : (AT_LEAST_UNI_SEMANTICS)
+                                     ? NREFFU
+                                     : (LOC)
+                                       ? NREFFL
+                                       : NREFF),
+                                num);
+                *flagp |= HASWIDTH;
+
+                /* override incorrect value set in reganode MJD */
+                Set_Node_Offset(ret, parse_start+1);
+                Set_Node_Cur_Length(ret, parse_start);
+                nextchar(pRExC_state);
+
+            }
+            break;
+       }
+       case 'g':
+       case '1': case '2': case '3': case '4':
+       case '5': case '6': case '7': case '8': case '9':
+           {
+               I32 num;
+               bool hasbrace = 0;
+
+               if (*RExC_parse == 'g') {
+                    bool isrel = 0;
+
+                   RExC_parse++;
+                   if (*RExC_parse == '{') {
+                       RExC_parse++;
+                       hasbrace = 1;
+                   }
+                   if (*RExC_parse == '-') {
+                       RExC_parse++;
+                       isrel = 1;
+                   }
+                   if (hasbrace && !isDIGIT(*RExC_parse)) {
+                       if (isrel) RExC_parse--;
+                        RExC_parse -= 2;
+                       goto parse_named_seq;
+                    }
+
+                    num = S_backref_value(RExC_parse);
+                    if (num == 0)
+                        vFAIL("Reference to invalid group 0");
+                    else if (num == I32_MAX) {
+                         if (isDIGIT(*RExC_parse))
+                           vFAIL("Reference to nonexistent group");
+                        else
+                            vFAIL("Unterminated \\g... pattern");
+                    }
+
+                    if (isrel) {
+                        num = RExC_npar - num;
+                        if (num < 1)
+                            vFAIL("Reference to nonexistent or unclosed group");
+                    }
+                }
+                else {
+                    num = S_backref_value(RExC_parse);
+                    /* bare \NNN might be backref or octal - if it is larger than or equal
+                     * RExC_npar then it is assumed to be and octal escape.
+                     * Note RExC_npar is +1 from the actual number of parens*/
+                    if (num == I32_MAX || (num > 9 && num >= RExC_npar
+                            && *RExC_parse != '8' && *RExC_parse != '9'))
+                    {
+                        /* Probably a character specified in octal, e.g. \35 */
+                        goto defchar;
+                    }
+                }
+
+                /* at this point RExC_parse definitely points to a backref
+                 * number */
+               {
+#ifdef RE_TRACK_PATTERN_OFFSETS
+                   char * const parse_start = RExC_parse - 1; /* MJD */
+#endif
+                   while (isDIGIT(*RExC_parse))
+                       RExC_parse++;
+                    if (hasbrace) {
+                        if (*RExC_parse != '}')
+                            vFAIL("Unterminated \\g{...} pattern");
+                        RExC_parse++;
+                    }
+                   if (!SIZE_ONLY) {
+                       if (num > (I32)RExC_rx->nparens)
+                           vFAIL("Reference to nonexistent group");
+                   }
+                   RExC_sawback = 1;
+                   ret = reganode(pRExC_state,
+                                  ((! FOLD)
+                                    ? REF
+                                    : (ASCII_FOLD_RESTRICTED)
+                                      ? REFFA
+                                       : (AT_LEAST_UNI_SEMANTICS)
+                                         ? REFFU
+                                         : (LOC)
+                                           ? REFFL
+                                           : REFF),
+                                   num);
+                   *flagp |= HASWIDTH;
+
+                    /* override incorrect value set in reganode MJD */
+                    Set_Node_Offset(ret, parse_start+1);
+                    Set_Node_Cur_Length(ret, parse_start);
+                   RExC_parse--;
+                   nextchar(pRExC_state);
+               }
+           }
+           break;
+       case '\0':
+           if (RExC_parse >= RExC_end)
+               FAIL("Trailing \\");
+           /* FALL THROUGH */
+       default:
+           /* Do not generate "unrecognized" warnings here, we fall
+              back into the quick-grab loop below */
+           parse_start--;
+           goto defchar;
+       }
+       break;
+
+    case '#':
+       if (RExC_flags & RXf_PMf_EXTENDED) {
+           if ( reg_skipcomment( pRExC_state ) )
+               goto tryagain;
+       }
+       /* FALL THROUGH */
+
+    default:
+
+            parse_start = RExC_parse - 1;
+
+           RExC_parse++;
+
+       defchar: {
+           STRLEN len = 0;
+           UV ender = 0;
+           char *p;
+           char *s;
+#define MAX_NODE_STRING_SIZE 127
+           char foldbuf[MAX_NODE_STRING_SIZE+UTF8_MAXBYTES_CASE];
+           char *s0;
+           U8 upper_parse = MAX_NODE_STRING_SIZE;
+            U8 node_type = compute_EXACTish(pRExC_state);
+            bool next_is_quantifier;
+            char * oldp = NULL;
+
+            /* We can convert EXACTF nodes to EXACTFU if they contain only
+             * characters that match identically regardless of the target
+             * string's UTF8ness.  The reason to do this is that EXACTF is not
+             * trie-able, EXACTFU is.
+             *
+             * Similarly, we can convert EXACTFL nodes to EXACTFU if they
+             * contain only above-Latin1 characters (hence must be in UTF8),
+             * which don't participate in folds with Latin1-range characters,
+             * as the latter's folds aren't known until runtime.  (We don't
+             * need to figure this out until pass 2) */
+            bool maybe_exactfu = PASS2
+                               && (node_type == EXACTF || node_type == EXACTFL);
+
+            /* If a folding node contains only code points that don't
+             * participate in folds, it can be changed into an EXACT node,
+             * which allows the optimizer more things to look for */
+            bool maybe_exact;
+
+           ret = reg_node(pRExC_state, node_type);
+
+            /* In pass1, folded, we use a temporary buffer instead of the
+             * actual node, as the node doesn't exist yet */
+           s = (SIZE_ONLY && FOLD) ? foldbuf : STRING(ret);
+
+            s0 = s;
+
+       reparse:
+
+            /* We do the EXACTFish to EXACT node only if folding.  (And we
+             * don't need to figure this out until pass 2) */
+            maybe_exact = FOLD && PASS2;
+
+           /* XXX The node can hold up to 255 bytes, yet this only goes to
+             * 127.  I (khw) do not know why.  Keeping it somewhat less than
+             * 255 allows us to not have to worry about overflow due to
+             * converting to utf8 and fold expansion, but that value is
+             * 255-UTF8_MAXBYTES_CASE.  join_exact() may join adjacent nodes
+             * split up by this limit into a single one using the real max of
+             * 255.  Even at 127, this breaks under rare circumstances.  If
+             * folding, we do not want to split a node at a character that is a
+             * non-final in a multi-char fold, as an input string could just
+             * happen to want to match across the node boundary.  The join
+             * would solve that problem if the join actually happens.  But a
+             * series of more than two nodes in a row each of 127 would cause
+             * the first join to succeed to get to 254, but then there wouldn't
+             * be room for the next one, which could at be one of those split
+             * multi-char folds.  I don't know of any fool-proof solution.  One
+             * could back off to end with only a code point that isn't such a
+             * non-final, but it is possible for there not to be any in the
+             * entire node. */
+           for (p = RExC_parse - 1;
+                len < upper_parse && p < RExC_end;
+                len++)
+           {
+               oldp = p;
+
+               if (RExC_flags & RXf_PMf_EXTENDED)
+                   p = regwhite( pRExC_state, p );
+               switch ((U8)*p) {
+               case '^':
+               case '$':
+               case '.':
+               case '[':
+               case '(':
+               case ')':
+               case '|':
+                   goto loopdone;
+               case '\\':
+                   /* Literal Escapes Switch
+
+                      This switch is meant to handle escape sequences that
+                      resolve to a literal character.
+
+                      Every escape sequence that represents something
+                      else, like an assertion or a char class, is handled
+                      in the switch marked 'Special Escapes' above in this
+                      routine, but also has an entry here as anything that
+                      isn't explicitly mentioned here will be treated as
+                      an unescaped equivalent literal.
+                   */
+
+                   switch ((U8)*++p) {
+                   /* These are all the special escapes. */
+                   case 'A':             /* Start assertion */
+                   case 'b': case 'B':   /* Word-boundary assertion*/
+                   case 'C':             /* Single char !DANGEROUS! */
+                   case 'd': case 'D':   /* digit class */
+                   case 'g': case 'G':   /* generic-backref, pos assertion */
+                   case 'h': case 'H':   /* HORIZWS */
+                   case 'k': case 'K':   /* named backref, keep marker */
+                   case 'p': case 'P':   /* Unicode property */
+                             case 'R':   /* LNBREAK */
+                   case 's': case 'S':   /* space class */
+                   case 'v': case 'V':   /* VERTWS */
+                   case 'w': case 'W':   /* word class */
+                    case 'X':             /* eXtended Unicode "combining
+                                             character sequence" */
+                   case 'z': case 'Z':   /* End of line/string assertion */
+                       --p;
+                       goto loopdone;
+
+                   /* Anything after here is an escape that resolves to a
+                      literal. (Except digits, which may or may not)
+                    */
+                   case 'n':
+                       ender = '\n';
+                       p++;
+                       break;
+                   case 'N': /* Handle a single-code point named character. */
+                        /* The options cause it to fail if a multiple code
+                         * point sequence.  Handle those in the switch() above
+                         * */
+                        RExC_parse = p + 1;
+                        if (! grok_bslash_N(pRExC_state, NULL, &ender,
+                                            flagp, depth, FALSE,
+                                            FALSE /* not strict */ ))
+                        {
+                            if (*flagp & RESTART_UTF8)
+                                FAIL("panic: grok_bslash_N set RESTART_UTF8");
+                            RExC_parse = p = oldp;
+                            goto loopdone;
+                        }
+                        p = RExC_parse;
+                        if (ender > 0xff) {
+                            REQUIRE_UTF8;
+                        }
+                        break;
+                   case 'r':
+                       ender = '\r';
+                       p++;
+                       break;
+                   case 't':
+                       ender = '\t';
+                       p++;
+                       break;
+                   case 'f':
+                       ender = '\f';
+                       p++;
+                       break;
+                   case 'e':
+                         ender = ASCII_TO_NATIVE('\033');
+                       p++;
+                       break;
+                   case 'a':
+                         ender = '\a';
+                       p++;
+                       break;
+                   case 'o':
+                       {
+                           UV result;
+                           const char* error_msg;
+
+                           bool valid = grok_bslash_o(&p,
+                                                      &result,
+                                                      &error_msg,
+                                                      TRUE, /* out warnings */
+                                                       FALSE, /* not strict */
+                                                       TRUE, /* Output warnings
+                                                                for non-
+                                                                portables */
+                                                       UTF);
+                           if (! valid) {
+                               RExC_parse = p; /* going to die anyway; point
+                                                  to exact spot of failure */
+                               vFAIL(error_msg);
+                           }
+                            ender = result;
+                           if (PL_encoding && ender < 0x100) {
+                               goto recode_encoding;
+                           }
+                           if (ender > 0xff) {
+                               REQUIRE_UTF8;
+                           }
+                           break;
+                       }
+                   case 'x':
+                       {
+                            UV result = UV_MAX; /* initialize to erroneous
+                                                   value */
+                           const char* error_msg;
+
+                           bool valid = grok_bslash_x(&p,
+                                                      &result,
+                                                      &error_msg,
+                                                      TRUE, /* out warnings */
+                                                       FALSE, /* not strict */
+                                                       TRUE, /* Output warnings
+                                                                for non-
+                                                                portables */
+                                                       UTF);
+                           if (! valid) {
+                               RExC_parse = p; /* going to die anyway; point
+                                                  to exact spot of failure */
+                               vFAIL(error_msg);
+                           }
+                            ender = result;
+
+                           if (PL_encoding && ender < 0x100) {
+                               goto recode_encoding;
+                           }
+                           if (ender > 0xff) {
+                               REQUIRE_UTF8;
+                           }
+                           break;
+                       }
+                   case 'c':
+                       p++;
+                       ender = grok_bslash_c(*p++, SIZE_ONLY);
+                       break;
+                    case '8': case '9': /* must be a backreference */
+                        --p;
+                        goto loopdone;
+                    case '1': case '2': case '3':case '4':
+                   case '5': case '6': case '7':
+                        /* When we parse backslash escapes there is ambiguity
+                         * between backreferences and octal escapes. Any escape
+                         * from \1 - \9 is a backreference, any multi-digit
+                         * escape which does not start with 0 and which when
+                         * evaluated as decimal could refer to an already
+                         * parsed capture buffer is a backslash. Anything else
+                         * is octal.
+                         *
+                         * Note this implies that \118 could be interpreted as
+                         * 118 OR as "\11" . "8" depending on whether there
+                         * were 118 capture buffers defined already in the
+                         * pattern.  */
+
+                        /* NOTE, RExC_npar is 1 more than the actual number of
+                         * parens we have seen so far, hence the < RExC_npar below. */
+
+                        if ( !isDIGIT(p[1]) || S_backref_value(p) < RExC_npar)
+                        {  /* Not to be treated as an octal constant, go
+                                   find backref */
+                            --p;
+                            goto loopdone;
+                        }
+                    case '0':
+                       {
+                           I32 flags = PERL_SCAN_SILENT_ILLDIGIT;
+                           STRLEN numlen = 3;
+                           ender = grok_oct(p, &numlen, &flags, NULL);
+                           if (ender > 0xff) {
+                               REQUIRE_UTF8;
+                           }
+                           p += numlen;
+                            if (SIZE_ONLY   /* like \08, \178 */
+                                && numlen < 3
+                                && p < RExC_end
+                                && isDIGIT(*p) && ckWARN(WARN_REGEXP))
+                            {
+                               reg_warn_non_literal_string(
+                                         p + 1,
+                                         form_short_octal_warning(p, numlen));
+                            }
+                       }
+                       if (PL_encoding && ender < 0x100)
+                           goto recode_encoding;
+                       break;
+                   recode_encoding:
+                       if (! RExC_override_recoding) {
+                           SV* enc = PL_encoding;
+                           ender = reg_recode((const char)(U8)ender, &enc);
+                           if (!enc && SIZE_ONLY)
+                               ckWARNreg(p, "Invalid escape in the specified encoding");
+                           REQUIRE_UTF8;
+                       }
+                       break;
+                   case '\0':
+                       if (p >= RExC_end)
+                           FAIL("Trailing \\");
+                       /* FALL THROUGH */
+                   default:
+                       if (!SIZE_ONLY&& isALPHANUMERIC(*p)) {
+                           /* Include any { following the alpha to emphasize
+                            * that it could be part of an escape at some point
+                            * in the future */
+                           int len = (isALPHA(*p) && *(p + 1) == '{') ? 2 : 1;
+                           ckWARN3reg(p + len, "Unrecognized escape \\%.*s passed through", len, p);
+                       }
+                       goto normal_default;
+                   } /* End of switch on '\' */
+                   break;
+               default:    /* A literal character */
+
+                    if (! SIZE_ONLY
+                        && RExC_flags & RXf_PMf_EXTENDED
+                        && ckWARN_d(WARN_DEPRECATED)
+                        && is_PATWS_non_low_safe(p, RExC_end, UTF))
+                    {
+                        vWARN_dep(p + ((UTF) ? UTF8SKIP(p) : 1),
+                                "Escape literal pattern white space under /x");
+                    }
+
+                 normal_default:
+                   if (UTF8_IS_START(*p) && UTF) {
+                       STRLEN numlen;
+                       ender = utf8n_to_uvchr((U8*)p, RExC_end - p,
+                                              &numlen, UTF8_ALLOW_DEFAULT);
+                       p += numlen;
+                   }
+                   else
+                       ender = (U8) *p++;
+                   break;
+               } /* End of switch on the literal */
+
+               /* Here, have looked at the literal character and <ender>
+                * contains its ordinal, <p> points to the character after it
+                */
+
+               if ( RExC_flags & RXf_PMf_EXTENDED)
+                   p = regwhite( pRExC_state, p );
+
+                /* If the next thing is a quantifier, it applies to this
+                 * character only, which means that this character has to be in
+                 * its own node and can't just be appended to the string in an
+                 * existing node, so if there are already other characters in
+                 * the node, close the node with just them, and set up to do
+                 * this character again next time through, when it will be the
+                 * only thing in its new node */
+                if ((next_is_quantifier = (p < RExC_end && ISMULT2(p))) && len)
+               {
+                    p = oldp;
+                    goto loopdone;
+                }
+
+                if (! FOLD   /* The simple case, just append the literal */
+                    || (LOC  /* Also don't fold for tricky chars under /l */
+                        && is_PROBLEMATIC_LOCALE_FOLD_cp(ender)))
+                {
+                    if (UTF) {
+
+                        /* Normally, we don't need the representation of the
+                         * character in the sizing pass--just its size, but if
+                         * folding, we have to actually put the character out
+                         * even in the sizing pass, because the size could
+                         * change as we juggle things at the end of this loop
+                         * to avoid splitting a too-full node in the middle of
+                         * a potential multi-char fold [perl #123539] */
+                        const STRLEN unilen = (SIZE_ONLY && ! FOLD)
+                                               ? UNISKIP(ender)
+                                               : (uvchr_to_utf8((U8*)s, ender) - (U8*)s);
+                        if (unilen > 0) {
+                           s   += unilen;
+                           len += unilen;
+                        }
+
+                        /* The loop increments <len> each time, as all but this
+                         * path (and one other) through it add a single byte to
+                         * the EXACTish node.  But this one has changed len to
+                         * be the correct final value, so subtract one to
+                         * cancel out the increment that follows */
+                        len--;
+                    }
+                    else if (FOLD) {
+                        /* See comment above for [perl #123539] */
+                        *(s++) = (char) ender;
+                    }
+                    else {
+                        REGC((char)ender, s++);
+                    }
+
+                    /* Can get here if folding only if is one of the /l
+                     * characters whose fold depends on the locale.  The
+                     * occurrence of any of these indicate that we can't
+                     * simplify things */
+                    if (FOLD) {
+                        maybe_exact = FALSE;
+                        maybe_exactfu = FALSE;
+                    }
+                }
+                else             /* FOLD */
+                     if (! ( UTF
+                        /* See comments for join_exact() as to why we fold this
+                         * non-UTF at compile time */
+                        || (node_type == EXACTFU
+                            && ender == LATIN_SMALL_LETTER_SHARP_S)))
+                {
+                    /* Here, are folding and are not UTF-8 encoded; therefore
+                     * the character must be in the range 0-255, and is not /l
+                     * (Not /l because we already handled these under /l in
+                     * is_PROBLEMATIC_LOCALE_FOLD_cp */
+                    if (IS_IN_SOME_FOLD_L1(ender)) {
+                        maybe_exact = FALSE;
+
+                        /* See if the character's fold differs between /d and
+                         * /u.  This includes the multi-char fold SHARP S to
+                         * 'ss' */
+                        if (maybe_exactfu
+                            && (PL_fold[ender] != PL_fold_latin1[ender]
+                                || ender == LATIN_SMALL_LETTER_SHARP_S
+                                || (len > 0
+                                   && isARG2_lower_or_UPPER_ARG1('s', ender)
+                                   && isARG2_lower_or_UPPER_ARG1('s',
+                                                                 *(s-1)))))
+                        {
+                            maybe_exactfu = FALSE;
+                        }
+                    }
+
+                    /* Even when folding, we store just the input character, as
+                     * we have an array that finds its fold quickly */
+                    *(s++) = (char) ender;
+                }
+                else {  /* FOLD and UTF */
+                    /* Unlike the non-fold case, we do actually have to
+                     * calculate the results here in pass 1.  This is for two
+                     * reasons, the folded length may be longer than the
+                     * unfolded, and we have to calculate how many EXACTish
+                     * nodes it will take; and we may run out of room in a node
+                     * in the middle of a potential multi-char fold, and have
+                     * to back off accordingly.  (Hence we can't use REGC for
+                     * the simple case just below.) */
+
+                    UV folded;
+                    if (isASCII(ender)) {
+                        folded = toFOLD(ender);
+                        *(s)++ = (U8) folded;
+                    }
+                    else {
+                        STRLEN foldlen;
+
+                        folded = _to_uni_fold_flags(
+                                     ender,
+                                     (U8 *) s,
+                                     &foldlen,
+                                     FOLD_FLAGS_FULL | ((ASCII_FOLD_RESTRICTED)
+                                                        ? FOLD_FLAGS_NOMIX_ASCII
+                                                        : 0));
+                        s += foldlen;
+
+                        /* The loop increments <len> each time, as all but this
+                         * path (and one other) through it add a single byte to
+                         * the EXACTish node.  But this one has changed len to
+                         * be the correct final value, so subtract one to
+                         * cancel out the increment that follows */
+                        len += foldlen - 1;
+                    }
+                    /* If this node only contains non-folding code points so
+                     * far, see if this new one is also non-folding */
+                    if (maybe_exact) {
+                        if (folded != ender) {
+                            maybe_exact = FALSE;
+                        }
+                        else {
+                            /* Here the fold is the original; we have to check
+                             * further to see if anything folds to it */
+                            if (_invlist_contains_cp(PL_utf8_foldable,
+                                                        ender))
+                            {
+                                maybe_exact = FALSE;
+                            }
+                        }
+                    }
+                    ender = folded;
+               }
+
+               if (next_is_quantifier) {
+
+                    /* Here, the next input is a quantifier, and to get here,
+                     * the current character is the only one in the node.
+                     * Also, here <len> doesn't include the final byte for this
+                     * character */
+                    len++;
+                    goto loopdone;
+               }
+
+           } /* End of loop through literal characters */
+
+            /* Here we have either exhausted the input or ran out of room in
+             * the node.  (If we encountered a character that can't be in the
+             * node, transfer is made directly to <loopdone>, and so we
+             * wouldn't have fallen off the end of the loop.)  In the latter
+             * case, we artificially have to split the node into two, because
+             * we just don't have enough space to hold everything.  This
+             * creates a problem if the final character participates in a
+             * multi-character fold in the non-final position, as a match that
+             * should have occurred won't, due to the way nodes are matched,
+             * and our artificial boundary.  So back off until we find a non-
+             * problematic character -- one that isn't at the beginning or
+             * middle of such a fold.  (Either it doesn't participate in any
+             * folds, or appears only in the final position of all the folds it
+             * does participate in.)  A better solution with far fewer false
+             * positives, and that would fill the nodes more completely, would
+             * be to actually have available all the multi-character folds to
+             * test against, and to back-off only far enough to be sure that
+             * this node isn't ending with a partial one.  <upper_parse> is set
+             * further below (if we need to reparse the node) to include just
+             * up through that final non-problematic character that this code
+             * identifies, so when it is set to less than the full node, we can
+             * skip the rest of this */
+            if (FOLD && p < RExC_end && upper_parse == MAX_NODE_STRING_SIZE) {
+
+                const STRLEN full_len = len;
+
+               assert(len >= MAX_NODE_STRING_SIZE);
+
+                /* Here, <s> points to the final byte of the final character.
+                 * Look backwards through the string until find a non-
+                 * problematic character */
+
+               if (! UTF) {
+
+                    /* This has no multi-char folds to non-UTF characters */
+                    if (ASCII_FOLD_RESTRICTED) {
+                        goto loopdone;
+                    }
+
+                    while (--s >= s0 && IS_NON_FINAL_FOLD(*s)) { }
+                    len = s - s0 + 1;
+               }
+                else {
+                    if (!  PL_NonL1NonFinalFold) {
+                        PL_NonL1NonFinalFold = _new_invlist_C_array(
+                                        NonL1_Perl_Non_Final_Folds_invlist);
+                    }
+
+                    /* Point to the first byte of the final character */
+                    s = (char *) utf8_hop((U8 *) s, -1);
+
+                    while (s >= s0) {   /* Search backwards until find
+                                           non-problematic char */
+                        if (UTF8_IS_INVARIANT(*s)) {
+
+                            /* There are no ascii characters that participate
+                             * in multi-char folds under /aa.  In EBCDIC, the
+                             * non-ascii invariants are all control characters,
+                             * so don't ever participate in any folds. */
+                            if (ASCII_FOLD_RESTRICTED
+                                || ! IS_NON_FINAL_FOLD(*s))
+                            {
+                                break;
+                            }
+                        }
+                        else if (UTF8_IS_DOWNGRADEABLE_START(*s)) {
+                            if (! IS_NON_FINAL_FOLD(TWO_BYTE_UTF8_TO_NATIVE(
+                                                                  *s, *(s+1))))
+                            {
+                                break;
+                            }
+                        }
+                        else if (! _invlist_contains_cp(
+                                        PL_NonL1NonFinalFold,
+                                        valid_utf8_to_uvchr((U8 *) s, NULL)))
+                        {
+                            break;
+                        }
+
+                        /* Here, the current character is problematic in that
+                         * it does occur in the non-final position of some
+                         * fold, so try the character before it, but have to
+                         * special case the very first byte in the string, so
+                         * we don't read outside the string */
+                        s = (s == s0) ? s -1 : (char *) utf8_hop((U8 *) s, -1);
+                    } /* End of loop backwards through the string */
+
+                    /* If there were only problematic characters in the string,
+                     * <s> will point to before s0, in which case the length
+                     * should be 0, otherwise include the length of the
+                     * non-problematic character just found */
+                    len = (s < s0) ? 0 : s - s0 + UTF8SKIP(s);
+               }
+
+                /* Here, have found the final character, if any, that is
+                 * non-problematic as far as ending the node without splitting
+                 * it across a potential multi-char fold.  <len> contains the
+                 * number of bytes in the node up-to and including that
+                 * character, or is 0 if there is no such character, meaning
+                 * the whole node contains only problematic characters.  In
+                 * this case, give up and just take the node as-is.  We can't
+                 * do any better */
+                if (len == 0) {
+                    len = full_len;
+
+                    /* If the node ends in an 's' we make sure it stays EXACTF,
+                     * as if it turns into an EXACTFU, it could later get
+                     * joined with another 's' that would then wrongly match
+                     * the sharp s */
+                    if (maybe_exactfu && isARG2_lower_or_UPPER_ARG1('s', ender))
+                    {
+                        maybe_exactfu = FALSE;
+                    }
+                } else {
+
+                    /* Here, the node does contain some characters that aren't
+                     * problematic.  If one such is the final character in the
+                     * node, we are done */
+                    if (len == full_len) {
+                        goto loopdone;
+                    }
+                    else if (len + ((UTF) ? UTF8SKIP(s) : 1) == full_len) {
+
+                        /* If the final character is problematic, but the
+                         * penultimate is not, back-off that last character to
+                         * later start a new node with it */
+                        p = oldp;
+                        goto loopdone;
+                    }
+
+                    /* Here, the final non-problematic character is earlier
+                     * in the input than the penultimate character.  What we do
+                     * is reparse from the beginning, going up only as far as
+                     * this final ok one, thus guaranteeing that the node ends
+                     * in an acceptable character.  The reason we reparse is
+                     * that we know how far in the character is, but we don't
+                     * know how to correlate its position with the input parse.
+                     * An alternate implementation would be to build that
+                     * correlation as we go along during the original parse,
+                     * but that would entail extra work for every node, whereas
+                     * this code gets executed only when the string is too
+                     * large for the node, and the final two characters are
+                     * problematic, an infrequent occurrence.  Yet another
+                     * possible strategy would be to save the tail of the
+                     * string, and the next time regatom is called, initialize
+                     * with that.  The problem with this is that unless you
+                     * back off one more character, you won't be guaranteed
+                     * regatom will get called again, unless regbranch,
+                     * regpiece ... are also changed.  If you do back off that
+                     * extra character, so that there is input guaranteed to
+                     * force calling regatom, you can't handle the case where
+                     * just the first character in the node is acceptable.  I
+                     * (khw) decided to try this method which doesn't have that
+                     * pitfall; if performance issues are found, we can do a
+                     * combination of the current approach plus that one */
+                    upper_parse = len;
+                    len = 0;
+                    s = s0;
+                    goto reparse;
+                }
+           }   /* End of verifying node ends with an appropriate char */
+
+       loopdone:   /* Jumped to when encounters something that shouldn't be in
+                      the node */
+
+            /* I (khw) don't know if you can get here with zero length, but the
+             * old code handled this situation by creating a zero-length EXACT
+             * node.  Might as well be NOTHING instead */
+            if (len == 0) {
+                OP(ret) = NOTHING;
+            }
+            else {
+                if (FOLD) {
+                    /* If 'maybe_exact' is still set here, means there are no
+                     * code points in the node that participate in folds;
+                     * similarly for 'maybe_exactfu' and code points that match
+                     * differently depending on UTF8ness of the target string
+                     * (for /u), or depending on locale for /l */
+                    if (maybe_exact) {
+                        OP(ret) = EXACT;
+                    }
+                    else if (maybe_exactfu) {
+                        OP(ret) = EXACTFU;
+                    }
+                }
+                alloc_maybe_populate_EXACT(pRExC_state, ret, flagp, len, ender,
+                                           FALSE /* Don't look to see if could
+                                                    be turned into an EXACT
+                                                    node, as we have already
+                                                    computed that */
+                                          );
+            }
+
+           RExC_parse = p - 1;
+            Set_Node_Cur_Length(ret, parse_start);
+           nextchar(pRExC_state);
+           {
+               /* len is STRLEN which is unsigned, need to copy to signed */
+               IV iv = len;
+               if (iv < 0)
+                   vFAIL("Internal disaster");
+           }
+
+       } /* End of label 'defchar:' */
+       break;
+    } /* End of giant switch on input character */
+
+    return(ret);
+}
+
+STATIC char *
+S_regwhite( RExC_state_t *pRExC_state, char *p )
+{
+    const char *e = RExC_end;
+
+    PERL_ARGS_ASSERT_REGWHITE;
+
+    while (p < e) {
+       if (isSPACE(*p))
+           ++p;
+       else if (*p == '#') {
+            bool ended = 0;
+           do {
+               if (*p++ == '\n') {
+                   ended = 1;
+                   break;
+               }
+           } while (p < e);
+           if (!ended)
+                RExC_seen |= REG_RUN_ON_COMMENT_SEEN;
+       }
+       else
+           break;
+    }
+    return p;
+}
+
+STATIC char *
+S_regpatws( RExC_state_t *pRExC_state, char *p , const bool recognize_comment )
+{
+    /* Returns the next non-pattern-white space, non-comment character (the
+     * latter only if 'recognize_comment is true) in the string p, which is
+     * ended by RExC_end.  If there is no line break ending a comment,
+     * RExC_seen has added the REG_RUN_ON_COMMENT_SEEN flag; */
+    const char *e = RExC_end;
+
+    PERL_ARGS_ASSERT_REGPATWS;
+
+    while (p < e) {
+        STRLEN len;
+       if ((len = is_PATWS_safe(p, e, UTF))) {
+           p += len;
+        }
+       else if (recognize_comment && *p == '#') {
+            bool ended = 0;
+           do {
+                p++;
+                if (is_LNBREAK_safe(p, e, UTF)) {
+                   ended = 1;
+                   break;
+               }
+           } while (p < e);
+           if (!ended)
+                RExC_seen |= REG_RUN_ON_COMMENT_SEEN;
+       }
+       else
+           break;
+    }
+    return p;
+}
+
+STATIC void
+S_populate_ANYOF_from_invlist(pTHX_ regnode *node, SV** invlist_ptr)
+{
+    /* Uses the inversion list '*invlist_ptr' to populate the ANYOF 'node'.  It
+     * sets up the bitmap and any flags, removing those code points from the
+     * inversion list, setting it to NULL should it become completely empty */
+
+    PERL_ARGS_ASSERT_POPULATE_ANYOF_FROM_INVLIST;
+    assert(PL_regkind[OP(node)] == ANYOF);
+
+    ANYOF_BITMAP_ZERO(node);
+    if (*invlist_ptr) {
+
+       /* This gets set if we actually need to modify things */
+       bool change_invlist = FALSE;
+
+       UV start, end;
+
+       /* Start looking through *invlist_ptr */
+       invlist_iterinit(*invlist_ptr);
+       while (invlist_iternext(*invlist_ptr, &start, &end)) {
+           UV high;
+           int i;
+
+            if (end == UV_MAX && start <= 256) {
+                ANYOF_FLAGS(node) |= ANYOF_ABOVE_LATIN1_ALL;
+            }
+            else if (end >= 256) {
+                ANYOF_FLAGS(node) |= ANYOF_UTF8;
+            }
+
+           /* Quit if are above what we should change */
+           if (start > 255) {
+               break;
+           }
+
+           change_invlist = TRUE;
+
+           /* Set all the bits in the range, up to the max that we are doing */
+           high = (end < 255) ? end : 255;
+           for (i = start; i <= (int) high; i++) {
+               if (! ANYOF_BITMAP_TEST(node, i)) {
+                   ANYOF_BITMAP_SET(node, i);
+               }
+           }
+       }
+       invlist_iterfinish(*invlist_ptr);
+
+        /* Done with loop; remove any code points that are in the bitmap from
+         * *invlist_ptr; similarly for code points above latin1 if we have a
+         * flag to match all of them anyways */
+       if (change_invlist) {
+           _invlist_subtract(*invlist_ptr, PL_Latin1, invlist_ptr);
+       }
+        if (ANYOF_FLAGS(node) & ANYOF_ABOVE_LATIN1_ALL) {
+           _invlist_intersection(*invlist_ptr, PL_Latin1, invlist_ptr);
+       }
+
+       /* If have completely emptied it, remove it completely */
+       if (_invlist_len(*invlist_ptr) == 0) {
+           SvREFCNT_dec_NN(*invlist_ptr);
+           *invlist_ptr = NULL;
+       }
+    }
+}
+
+/* Parse POSIX character classes: [[:foo:]], [[=foo=]], [[.foo.]].
+   Character classes ([:foo:]) can also be negated ([:^foo:]).
+   Returns a named class id (ANYOF_XXX) if successful, -1 otherwise.
+   Equivalence classes ([=foo=]) and composites ([.foo.]) are parsed,
+   but trigger failures because they are currently unimplemented. */
+
+#define POSIXCC_DONE(c)   ((c) == ':')
+#define POSIXCC_NOTYET(c) ((c) == '=' || (c) == '.')
+#define POSIXCC(c) (POSIXCC_DONE(c) || POSIXCC_NOTYET(c))
+
+PERL_STATIC_INLINE I32
+S_regpposixcc(pTHX_ RExC_state_t *pRExC_state, I32 value, const bool strict)
+{
+    dVAR;
+    I32 namedclass = OOB_NAMEDCLASS;
+
+    PERL_ARGS_ASSERT_REGPPOSIXCC;
+
+    if (value == '[' && RExC_parse + 1 < RExC_end &&
+       /* I smell either [: or [= or [. -- POSIX has been here, right? */
+       POSIXCC(UCHARAT(RExC_parse)))
+    {
+       const char c = UCHARAT(RExC_parse);
+       char* const s = RExC_parse++;
+
+       while (RExC_parse < RExC_end && UCHARAT(RExC_parse) != c)
+           RExC_parse++;
+       if (RExC_parse == RExC_end) {
+            if (strict) {
+
+                /* Try to give a better location for the error (than the end of
+                 * the string) by looking for the matching ']' */
+                RExC_parse = s;
+                while (RExC_parse < RExC_end && UCHARAT(RExC_parse) != ']') {
+                    RExC_parse++;
+                }
+                vFAIL2("Unmatched '%c' in POSIX class", c);
+            }
+           /* Grandfather lone [:, [=, [. */
+           RExC_parse = s;
+        }
+       else {
+           const char* const t = RExC_parse++; /* skip over the c */
+           assert(*t == c);
+
+           if (UCHARAT(RExC_parse) == ']') {
+               const char *posixcc = s + 1;
+               RExC_parse++; /* skip over the ending ] */
+
+               if (*s == ':') {
+                   const I32 complement = *posixcc == '^' ? *posixcc++ : 0;
+                   const I32 skip = t - posixcc;
+
+                   /* Initially switch on the length of the name.  */
+                   switch (skip) {
+                   case 4:
+                        if (memEQ(posixcc, "word", 4)) /* this is not POSIX,
+                                                          this is the Perl \w
+                                                        */
+                           namedclass = ANYOF_WORDCHAR;
+                       break;
+                   case 5:
+                       /* Names all of length 5.  */
+                       /* alnum alpha ascii blank cntrl digit graph lower
+                          print punct space upper  */
+                       /* Offset 4 gives the best switch position.  */
+                       switch (posixcc[4]) {
+                       case 'a':
+                           if (memEQ(posixcc, "alph", 4)) /* alpha */
+                               namedclass = ANYOF_ALPHA;
+                           break;
+                       case 'e':
+                           if (memEQ(posixcc, "spac", 4)) /* space */
+                               namedclass = ANYOF_PSXSPC;
+                           break;
+                       case 'h':
+                           if (memEQ(posixcc, "grap", 4)) /* graph */
+                               namedclass = ANYOF_GRAPH;
+                           break;
+                       case 'i':
+                           if (memEQ(posixcc, "asci", 4)) /* ascii */
+                               namedclass = ANYOF_ASCII;
+                           break;
+                       case 'k':
+                           if (memEQ(posixcc, "blan", 4)) /* blank */
+                               namedclass = ANYOF_BLANK;
+                           break;
+                       case 'l':
+                           if (memEQ(posixcc, "cntr", 4)) /* cntrl */
+                               namedclass = ANYOF_CNTRL;
+                           break;
+                       case 'm':
+                           if (memEQ(posixcc, "alnu", 4)) /* alnum */
+                               namedclass = ANYOF_ALPHANUMERIC;
+                           break;
+                       case 'r':
+                           if (memEQ(posixcc, "lowe", 4)) /* lower */
+                               namedclass = (FOLD) ? ANYOF_CASED : ANYOF_LOWER;
+                           else if (memEQ(posixcc, "uppe", 4)) /* upper */
+                               namedclass = (FOLD) ? ANYOF_CASED : ANYOF_UPPER;
+                           break;
+                       case 't':
+                           if (memEQ(posixcc, "digi", 4)) /* digit */
+                               namedclass = ANYOF_DIGIT;
+                           else if (memEQ(posixcc, "prin", 4)) /* print */
+                               namedclass = ANYOF_PRINT;
+                           else if (memEQ(posixcc, "punc", 4)) /* punct */
+                               namedclass = ANYOF_PUNCT;
+                           break;
+                       }
+                       break;
+                   case 6:
+                       if (memEQ(posixcc, "xdigit", 6))
+                           namedclass = ANYOF_XDIGIT;
+                       break;
+                   }
+
+                   if (namedclass == OOB_NAMEDCLASS)
+                       vFAIL2utf8f(
+                            "POSIX class [:%"UTF8f":] unknown",
+                           UTF8fARG(UTF, t - s - 1, s + 1));
+
+                    /* The #defines are structured so each complement is +1 to
+                     * the normal one */
+                    if (complement) {
+                        namedclass++;
+                    }
+                   assert (posixcc[skip] == ':');
+                   assert (posixcc[skip+1] == ']');
+               } else if (!SIZE_ONLY) {
+                   /* [[=foo=]] and [[.foo.]] are still future. */
+
+                   /* adjust RExC_parse so the warning shows after
+                      the class closes */
+                   while (UCHARAT(RExC_parse) && UCHARAT(RExC_parse) != ']')
+                       RExC_parse++;
+                   vFAIL3("POSIX syntax [%c %c] is reserved for future extensions", c, c);
+               }
+           } else {
+               /* Maternal grandfather:
+                * "[:" ending in ":" but not in ":]" */
+                if (strict) {
+                    vFAIL("Unmatched '[' in POSIX class");
+                }
+
+                /* Grandfather lone [:, [=, [. */
+               RExC_parse = s;
+           }
+       }
+    }
+
+    return namedclass;
+}
+
+STATIC bool
+S_could_it_be_a_POSIX_class(pTHX_ RExC_state_t *pRExC_state)
+{
+    /* This applies some heuristics at the current parse position (which should
+     * be at a '[') to see if what follows might be intended to be a [:posix:]
+     * class.  It returns true if it really is a posix class, of course, but it
+     * also can return true if it thinks that what was intended was a posix
+     * class that didn't quite make it.
+     *
+     * It will return true for
+     *      [:alphanumerics:
+     *      [:alphanumerics]  (as long as the ] isn't followed immediately by a
+     *                         ')' indicating the end of the (?[
+     *      [:any garbage including %^&$ punctuation:]
+     *
+     * This is designed to be called only from S_handle_regex_sets; it could be
+     * easily adapted to be called from the spot at the beginning of regclass()
+     * that checks to see in a normal bracketed class if the surrounding []
+     * have been omitted ([:word:] instead of [[:word:]]).  But doing so would
+     * change long-standing behavior, so I (khw) didn't do that */
+    char* p = RExC_parse + 1;
+    char first_char = *p;
+
+    PERL_ARGS_ASSERT_COULD_IT_BE_A_POSIX_CLASS;
+
+    assert(*(p - 1) == '[');
+
+    if (! POSIXCC(first_char)) {
+        return FALSE;
+    }
+
+    p++;
+    while (p < RExC_end && isWORDCHAR(*p)) p++;
+
+    if (p >= RExC_end) {
+        return FALSE;
+    }
+
+    if (p - RExC_parse > 2    /* Got at least 1 word character */
+        && (*p == first_char
+            || (*p == ']' && p + 1 < RExC_end && *(p + 1) != ')')))
+    {
+        return TRUE;
+    }
+
+    p = (char *) memchr(RExC_parse, ']', RExC_end - RExC_parse);
+
+    return (p
+            && p - RExC_parse > 2 /* [:] evaluates to colon;
+                                      [::] is a bad posix class. */
+            && first_char == *(p - 1));
+}
+
+STATIC regnode *
+S_handle_regex_sets(pTHX_ RExC_state_t *pRExC_state, SV** return_invlist,
+                    I32 *flagp, U32 depth,
+                    char * const oregcomp_parse)
+{
+    /* Handle the (?[...]) construct to do set operations */
+
+    U8 curchar;
+    UV start, end;     /* End points of code point ranges */
+    SV* result_string;
+    char *save_end, *save_parse;
+    SV* final;
+    STRLEN len;
+    regnode* node;
+    AV* stack;
+    const bool save_fold = FOLD;
+
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_HANDLE_REGEX_SETS;
+
+    if (LOC) {
+        vFAIL("(?[...]) not valid in locale");
+    }
+    RExC_uni_semantics = 1;
+
+    /* This will return only an ANYOF regnode, or (unlikely) something smaller
+     * (such as EXACT).  Thus we can skip most everything if just sizing.  We
+     * call regclass to handle '[]' so as to not have to reinvent its parsing
+     * rules here (throwing away the size it computes each time).  And, we exit
+     * upon an unescaped ']' that isn't one ending a regclass.  To do both
+     * these things, we need to realize that something preceded by a backslash
+     * is escaped, so we have to keep track of backslashes */
+    if (SIZE_ONLY) {
+        UV depth = 0; /* how many nested (?[...]) constructs */
+
+        Perl_ck_warner_d(aTHX_
+            packWARN(WARN_EXPERIMENTAL__REGEX_SETS),
+            "The regex_sets feature is experimental" REPORT_LOCATION,
+                UTF8fARG(UTF, (RExC_parse - RExC_precomp), RExC_precomp),
+                UTF8fARG(UTF,
+                         RExC_end - RExC_start - (RExC_parse - RExC_precomp),
+                         RExC_precomp + (RExC_parse - RExC_precomp)));
+
+        while (RExC_parse < RExC_end) {
+            SV* current = NULL;
+            RExC_parse = regpatws(pRExC_state, RExC_parse,
+                                TRUE); /* means recognize comments */
+            switch (*RExC_parse) {
+                case '?':
+                    if (RExC_parse[1] == '[') depth++, RExC_parse++;
+                    /* FALL THROUGH */
+                default:
+                    break;
+                case '\\':
+                    /* Skip the next byte (which could cause us to end up in
+                     * the middle of a UTF-8 character, but since none of those
+                     * are confusable with anything we currently handle in this
+                     * switch (invariants all), it's safe.  We'll just hit the
+                     * default: case next time and keep on incrementing until
+                     * we find one of the invariants we do handle. */
+                    RExC_parse++;
+                    break;
+                case '[':
+                {
+                    /* If this looks like it is a [:posix:] class, leave the
+                     * parse pointer at the '[' to fool regclass() into
+                     * thinking it is part of a '[[:posix:]]'.  That function
+                     * will use strict checking to force a syntax error if it
+                     * doesn't work out to a legitimate class */
+                    bool is_posix_class
+                                    = could_it_be_a_POSIX_class(pRExC_state);
+                    if (! is_posix_class) {
+                        RExC_parse++;
+                    }
+
+                    /* regclass() can only return RESTART_UTF8 if multi-char
+                       folds are allowed.  */
+                    if (!regclass(pRExC_state, flagp,depth+1,
+                                  is_posix_class, /* parse the whole char
+                                                     class only if not a
+                                                     posix class */
+                                  FALSE, /* don't allow multi-char folds */
+                                  TRUE, /* silence non-portable warnings. */
+                                  &current))
+                        FAIL2("panic: regclass returned NULL to handle_sets, flags=%#"UVxf"",
+                              (UV) *flagp);
+
+                    /* function call leaves parse pointing to the ']', except
+                     * if we faked it */
+                    if (is_posix_class) {
+                        RExC_parse--;
+                    }
+
+                    SvREFCNT_dec(current);   /* In case it returned something */
+                    break;
+                }
+
+                case ']':
+                    if (depth--) break;
+                    RExC_parse++;
+                    if (RExC_parse < RExC_end
+                        && *RExC_parse == ')')
+                    {
+                        node = reganode(pRExC_state, ANYOF, 0);
+                        RExC_size += ANYOF_SKIP;
+                        nextchar(pRExC_state);
+                        Set_Node_Length(node,
+                                RExC_parse - oregcomp_parse + 1); /* MJD */
+                        return node;
+                    }
+                    goto no_close;
+            }
+            RExC_parse++;
+        }
+
+        no_close:
+        FAIL("Syntax error in (?[...])");
+    }
+
+    /* Pass 2 only after this.  Everything in this construct is a
+     * metacharacter.  Operands begin with either a '\' (for an escape
+     * sequence), or a '[' for a bracketed character class.  Any other
+     * character should be an operator, or parenthesis for grouping.  Both
+     * types of operands are handled by calling regclass() to parse them.  It
+     * is called with a parameter to indicate to return the computed inversion
+     * list.  The parsing here is implemented via a stack.  Each entry on the
+     * stack is a single character representing one of the operators, or the
+     * '('; or else a pointer to an operand inversion list. */
+
+#define IS_OPERAND(a)  (! SvIOK(a))
+
+    /* The stack starts empty.  It is a syntax error if the first thing parsed
+     * is a binary operator; everything else is pushed on the stack.  When an
+     * operand is parsed, the top of the stack is examined.  If it is a binary
+     * operator, the item before it should be an operand, and both are replaced
+     * by the result of doing that operation on the new operand and the one on
+     * the stack.   Thus a sequence of binary operands is reduced to a single
+     * one before the next one is parsed.
+     *
+     * A unary operator may immediately follow a binary in the input, for
+     * example
+     *      [a] + ! [b]
+     * When an operand is parsed and the top of the stack is a unary operator,
+     * the operation is performed, and then the stack is rechecked to see if
+     * this new operand is part of a binary operation; if so, it is handled as
+     * above.
+     *
+     * A '(' is simply pushed on the stack; it is valid only if the stack is
+     * empty, or the top element of the stack is an operator or another '('
+     * (for which the parenthesized expression will become an operand).  By the
+     * time the corresponding ')' is parsed everything in between should have
+     * been parsed and evaluated to a single operand (or else is a syntax
+     * error), and is handled as a regular operand */
+
+    sv_2mortal((SV *)(stack = newAV()));
+
+    while (RExC_parse < RExC_end) {
+        I32 top_index = av_tindex(stack);
+        SV** top_ptr;
+        SV* current = NULL;
+
+        /* Skip white space */
+        RExC_parse = regpatws(pRExC_state, RExC_parse,
+                                TRUE); /* means recognize comments */
+        if (RExC_parse >= RExC_end) {
+            Perl_croak(aTHX_ "panic: Read past end of '(?[ ])'");
+        }
+        if ((curchar = UCHARAT(RExC_parse)) == ']') {
+            break;
+        }
+
+        switch (curchar) {
+
+            case '?':
+                if (av_tindex(stack) >= 0   /* This makes sure that we can
+                                               safely subtract 1 from
+                                               RExC_parse in the next clause.
+                                               If we have something on the
+                                               stack, we have parsed something
+                                             */
+                    && UCHARAT(RExC_parse - 1) == '('
+                    && RExC_parse < RExC_end)
+                {
+                    /* If is a '(?', could be an embedded '(?flags:(?[...])'.
+                     * This happens when we have some thing like
+                     *
+                     *   my $thai_or_lao = qr/(?[ \p{Thai} + \p{Lao} ])/;
+                     *   ...
+                     *   qr/(?[ \p{Digit} & $thai_or_lao ])/;
+                     *
+                     * Here we would be handling the interpolated
+                     * '$thai_or_lao'.  We handle this by a recursive call to
+                     * ourselves which returns the inversion list the
+                     * interpolated expression evaluates to.  We use the flags
+                     * from the interpolated pattern. */
+                    U32 save_flags = RExC_flags;
+                    const char * const save_parse = ++RExC_parse;
+
+                    parse_lparen_question_flags(pRExC_state);
+
+                    if (RExC_parse == save_parse  /* Makes sure there was at
+                                                     least one flag (or this
+                                                     embedding wasn't compiled)
+                                                   */
+                        || RExC_parse >= RExC_end - 4
+                        || UCHARAT(RExC_parse) != ':'
+                        || UCHARAT(++RExC_parse) != '('
+                        || UCHARAT(++RExC_parse) != '?'
+                        || UCHARAT(++RExC_parse) != '[')
+                    {
+
+                        /* In combination with the above, this moves the
+                         * pointer to the point just after the first erroneous
+                         * character (or if there are no flags, to where they
+                         * should have been) */
+                        if (RExC_parse >= RExC_end - 4) {
+                            RExC_parse = RExC_end;
+                        }
+                        else if (RExC_parse != save_parse) {
+                            RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+                        }
+                        vFAIL("Expecting '(?flags:(?[...'");
+                    }
+                    RExC_parse++;
+                    (void) handle_regex_sets(pRExC_state, &current, flagp,
+                                                    depth+1, oregcomp_parse);
+
+                    /* Here, 'current' contains the embedded expression's
+                     * inversion list, and RExC_parse points to the trailing
+                     * ']'; the next character should be the ')' which will be
+                     * paired with the '(' that has been put on the stack, so
+                     * the whole embedded expression reduces to '(operand)' */
+                    RExC_parse++;
+
+                    RExC_flags = save_flags;
+                    goto handle_operand;
+                }
+                /* FALL THROUGH */
+
+            default:
+                RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+                vFAIL("Unexpected character");
+
+            case '\\':
+                /* regclass() can only return RESTART_UTF8 if multi-char
+                   folds are allowed.  */
+                if (!regclass(pRExC_state, flagp,depth+1,
+                              TRUE, /* means parse just the next thing */
+                              FALSE, /* don't allow multi-char folds */
+                              FALSE, /* don't silence non-portable warnings.  */
+                              &current))
+                    FAIL2("panic: regclass returned NULL to handle_sets, flags=%#"UVxf"",
+                          (UV) *flagp);
+                /* regclass() will return with parsing just the \ sequence,
+                 * leaving the parse pointer at the next thing to parse */
+                RExC_parse--;
+                goto handle_operand;
+
+            case '[':   /* Is a bracketed character class */
+            {
+                bool is_posix_class = could_it_be_a_POSIX_class(pRExC_state);
+
+                if (! is_posix_class) {
+                    RExC_parse++;
+                }
+
+                /* regclass() can only return RESTART_UTF8 if multi-char
+                   folds are allowed.  */
+                if(!regclass(pRExC_state, flagp,depth+1,
+                             is_posix_class, /* parse the whole char class
+                                                only if not a posix class */
+                             FALSE, /* don't allow multi-char folds */
+                             FALSE, /* don't silence non-portable warnings.  */
+                             &current))
+                    FAIL2("panic: regclass returned NULL to handle_sets, flags=%#"UVxf"",
+                          (UV) *flagp);
+                /* function call leaves parse pointing to the ']', except if we
+                 * faked it */
+                if (is_posix_class) {
+                    RExC_parse--;
+                }
+
+                goto handle_operand;
+            }
+
+            case '&':
+            case '|':
+            case '+':
+            case '-':
+            case '^':
+                if (top_index < 0
+                    || ( ! (top_ptr = av_fetch(stack, top_index, FALSE)))
+                    || ! IS_OPERAND(*top_ptr))
+                {
+                    RExC_parse++;
+                    vFAIL2("Unexpected binary operator '%c' with no preceding operand", curchar);
+                }
+                av_push(stack, newSVuv(curchar));
+                break;
+
+            case '!':
+                av_push(stack, newSVuv(curchar));
+                break;
+
+            case '(':
+                if (top_index >= 0) {
+                    top_ptr = av_fetch(stack, top_index, FALSE);
+                    assert(top_ptr);
+                    if (IS_OPERAND(*top_ptr)) {
+                        RExC_parse++;
+                        vFAIL("Unexpected '(' with no preceding operator");
+                    }
+                }
+                av_push(stack, newSVuv(curchar));
+                break;
+
+            case ')':
+            {
+                SV* lparen;
+                if (top_index < 1
+                    || ! (current = av_pop(stack))
+                    || ! IS_OPERAND(current)
+                    || ! (lparen = av_pop(stack))
+                    || IS_OPERAND(lparen)
+                    || SvUV(lparen) != '(')
+                {
+                    SvREFCNT_dec(current);
+                    RExC_parse++;
+                    vFAIL("Unexpected ')'");
+                }
+                top_index -= 2;
+                SvREFCNT_dec_NN(lparen);
+
+                /* FALL THROUGH */
+            }
+
+              handle_operand:
+
+                /* Here, we have an operand to process, in 'current' */
+
+                if (top_index < 0) {    /* Just push if stack is empty */
+                    av_push(stack, current);
+                }
+                else {
+                    SV* top = av_pop(stack);
+                    SV *prev = NULL;
+                    char current_operator;
+
+                    if (IS_OPERAND(top)) {
+                        SvREFCNT_dec_NN(top);
+                        SvREFCNT_dec_NN(current);
+                        vFAIL("Operand with no preceding operator");
+                    }
+                    current_operator = (char) SvUV(top);
+                    switch (current_operator) {
+                        case '(':   /* Push the '(' back on followed by the new
+                                       operand */
+                            av_push(stack, top);
+                            av_push(stack, current);
+                            SvREFCNT_inc(top);  /* Counters the '_dec' done
+                                                   just after the 'break', so
+                                                   it doesn't get wrongly freed
+                                                 */
+                            break;
+
+                        case '!':
+                            _invlist_invert(current);
+
+                            /* Unlike binary operators, the top of the stack,
+                             * now that this unary one has been popped off, may
+                             * legally be an operator, and we now have operand
+                             * for it. */
+                            top_index--;
+                            SvREFCNT_dec_NN(top);
+                            goto handle_operand;
+
+                        case '&':
+                            prev = av_pop(stack);
+                            _invlist_intersection(prev,
+                                                   current,
+                                                   &current);
+                            av_push(stack, current);
+                            break;
+
+                        case '|':
+                        case '+':
+                            prev = av_pop(stack);
+                            _invlist_union(prev, current, &current);
+                            av_push(stack, current);
+                            break;
+
+                        case '-':
+                            prev = av_pop(stack);;
+                            _invlist_subtract(prev, current, &current);
+                            av_push(stack, current);
+                            break;
+
+                        case '^':   /* The union minus the intersection */
+                        {
+                            SV* i = NULL;
+                            SV* u = NULL;
+                            SV* element;
+
+                            prev = av_pop(stack);
+                            _invlist_union(prev, current, &u);
+                            _invlist_intersection(prev, current, &i);
+                            /* _invlist_subtract will overwrite current
+                                without freeing what it already contains */
+                            element = current;
+                            _invlist_subtract(u, i, &current);
+                            av_push(stack, current);
+                            SvREFCNT_dec_NN(i);
+                            SvREFCNT_dec_NN(u);
+                            SvREFCNT_dec_NN(element);
+                            break;
+                        }
+
+                        default:
+                            Perl_croak(aTHX_ "panic: Unexpected item on '(?[ ])' stack");
+                }
+                SvREFCNT_dec_NN(top);
+                SvREFCNT_dec(prev);
+            }
+        }
+
+        RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+    }
+
+    if (av_tindex(stack) < 0   /* Was empty */
+        || ((final = av_pop(stack)) == NULL)
+        || ! IS_OPERAND(final)
+        || av_tindex(stack) >= 0)  /* More left on stack */
+    {
+        vFAIL("Incomplete expression within '(?[ ])'");
+    }
+
+    /* Here, 'final' is the resultant inversion list from evaluating the
+     * expression.  Return it if so requested */
+    if (return_invlist) {
+        *return_invlist = final;
+        return END;
+    }
+
+    /* Otherwise generate a resultant node, based on 'final'.  regclass() is
+     * expecting a string of ranges and individual code points */
+    invlist_iterinit(final);
+    result_string = newSVpvs("");
+    while (invlist_iternext(final, &start, &end)) {
+        if (start == end) {
+            Perl_sv_catpvf(aTHX_ result_string, "\\x{%"UVXf"}", start);
+        }
+        else {
+            Perl_sv_catpvf(aTHX_ result_string, "\\x{%"UVXf"}-\\x{%"UVXf"}",
+                                                     start,          end);
+        }
+    }
+
+    save_parse = RExC_parse;
+    RExC_parse = SvPV(result_string, len);
+    save_end = RExC_end;
+    RExC_end = RExC_parse + len;
+
+    /* We turn off folding around the call, as the class we have constructed
+     * already has all folding taken into consideration, and we don't want
+     * regclass() to add to that */
+    RExC_flags &= ~RXf_PMf_FOLD;
+    /* regclass() can only return RESTART_UTF8 if multi-char folds are allowed.
+     */
+    node = regclass(pRExC_state, flagp,depth+1,
+                    FALSE, /* means parse the whole char class */
+                    FALSE, /* don't allow multi-char folds */
+                    TRUE, /* silence non-portable warnings.  The above may very
+                             well have generated non-portable code points, but
+                             they're valid on this machine */
+                    NULL);
+    if (!node)
+        FAIL2("panic: regclass returned NULL to handle_sets, flags=%#"UVxf,
+                    PTR2UV(flagp));
+    if (save_fold) {
+        RExC_flags |= RXf_PMf_FOLD;
+    }
+    RExC_parse = save_parse + 1;
+    RExC_end = save_end;
+    SvREFCNT_dec_NN(final);
+    SvREFCNT_dec_NN(result_string);
+
+    nextchar(pRExC_state);
+    Set_Node_Length(node, RExC_parse - oregcomp_parse + 1); /* MJD */
+    return node;
+}
+#undef IS_OPERAND
+
+/* The names of properties whose definitions are not known at compile time are
+ * stored in this SV, after a constant heading.  So if the length has been
+ * changed since initialization, then there is a run-time definition. */
+#define HAS_NONLOCALE_RUNTIME_PROPERTY_DEFINITION                            \
+                                        (SvCUR(listsv) != initial_listsv_len)
+
+STATIC regnode *
+S_regclass(pTHX_ RExC_state_t *pRExC_state, I32 *flagp, U32 depth,
+                 const bool stop_at_1,  /* Just parse the next thing, don't
+                                           look for a full character class */
+                 bool allow_multi_folds,
+                 const bool silence_non_portable,   /* Don't output warnings
+                                                       about too large
+                                                       characters */
+                 SV** ret_invlist)  /* Return an inversion list, not a node */
+{
+    /* parse a bracketed class specification.  Most of these will produce an
+     * ANYOF node; but something like [a] will produce an EXACT node; [aA], an
+     * EXACTFish node; [[:ascii:]], a POSIXA node; etc.  It is more complex
+     * under /i with multi-character folds: it will be rewritten following the
+     * paradigm of this example, where the <multi-fold>s are characters which
+     * fold to multiple character sequences:
+     *      /[abc\x{multi-fold1}def\x{multi-fold2}ghi]/i
+     * gets effectively rewritten as:
+     *      /(?:\x{multi-fold1}|\x{multi-fold2}|[abcdefghi]/i
+     * reg() gets called (recursively) on the rewritten version, and this
+     * function will return what it constructs.  (Actually the <multi-fold>s
+     * aren't physically removed from the [abcdefghi], it's just that they are
+     * ignored in the recursion by means of a flag:
+     * <RExC_in_multi_char_class>.)
+     *
+     * ANYOF nodes contain a bit map for the first 256 characters, with the
+     * corresponding bit set if that character is in the list.  For characters
+     * above 255, a range list or swash is used.  There are extra bits for \w,
+     * etc. in locale ANYOFs, as what these match is not determinable at
+     * compile time
+     *
+     * Returns NULL, setting *flagp to RESTART_UTF8 if the sizing scan needs
+     * to be restarted.  This can only happen if ret_invlist is non-NULL.
+     */
+
+    dVAR;
+    UV prevvalue = OOB_UNICODE, save_prevvalue = OOB_UNICODE;
+    IV range = 0;
+    UV value = OOB_UNICODE, save_value = OOB_UNICODE;
+    regnode *ret;
+    STRLEN numlen;
+    IV namedclass = OOB_NAMEDCLASS;
+    char *rangebegin = NULL;
+    bool need_class = 0;
+    SV *listsv = NULL;
+    STRLEN initial_listsv_len = 0; /* Kind of a kludge to see if it is more
+                                     than just initialized.  */
+    SV* properties = NULL;    /* Code points that match \p{} \P{} */
+    SV* posixes = NULL;     /* Code points that match classes like [:word:],
+                               extended beyond the Latin1 range.  These have to
+                               be kept separate from other code points for much
+                               of this function because their handling  is
+                               different under /i, and for most classes under
+                               /d as well */
+    SV* nposixes = NULL;    /* Similarly for [:^word:].  These are kept
+                               separate for a while from the non-complemented
+                               versions because of complications with /d
+                               matching */
+    UV element_count = 0;   /* Number of distinct elements in the class.
+                              Optimizations may be possible if this is tiny */
+    AV * multi_char_matches = NULL; /* Code points that fold to more than one
+                                       character; used under /i */
+    UV n;
+    char * stop_ptr = RExC_end;    /* where to stop parsing */
+    const bool skip_white = cBOOL(ret_invlist); /* ignore unescaped white
+                                                   space? */
+    const bool strict = cBOOL(ret_invlist); /* Apply strict parsing rules? */
+
+    /* Unicode properties are stored in a swash; this holds the current one
+     * being parsed.  If this swash is the only above-latin1 component of the
+     * character class, an optimization is to pass it directly on to the
+     * execution engine.  Otherwise, it is set to NULL to indicate that there
+     * are other things in the class that have to be dealt with at execution
+     * time */
+    SV* swash = NULL;          /* Code points that match \p{} \P{} */
+
+    /* Set if a component of this character class is user-defined; just passed
+     * on to the engine */
+    bool has_user_defined_property = FALSE;
+
+    /* inversion list of code points this node matches only when the target
+     * string is in UTF-8.  (Because is under /d) */
+    SV* depends_list = NULL;
+
+    /* Inversion list of code points this node matches regardless of things
+     * like locale, folding, utf8ness of the target string */
+    SV* cp_list = NULL;
+
+    /* Like cp_list, but code points on this list need to be checked for things
+     * that fold to/from them under /i */
+    SV* cp_foldable_list = NULL;
+
+    /* Like cp_list, but code points on this list are valid only when the
+     * runtime locale is UTF-8 */
+    SV* only_utf8_locale_list = NULL;
+
+#ifdef EBCDIC
+    /* In a range, counts how many 0-2 of the ends of it came from literals,
+     * not escapes.  Thus we can tell if 'A' was input vs \x{C1} */
+    UV literal_endpoint = 0;
+#endif
+    bool invert = FALSE;    /* Is this class to be complemented */
+
+    bool warn_super = ALWAYS_WARN_SUPER;
+
+    regnode * const orig_emit = RExC_emit; /* Save the original RExC_emit in
+        case we need to change the emitted regop to an EXACT. */
+    const char * orig_parse = RExC_parse;
+    const SSize_t orig_size = RExC_size;
+    bool posixl_matches_all = FALSE; /* Does /l class have both e.g. \W,\w ? */
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGCLASS;
+#ifndef DEBUGGING
+    PERL_UNUSED_ARG(depth);
+#endif
+
+    DEBUG_PARSE("clas");
+
+    /* Assume we are going to generate an ANYOF node. */
+    ret = reganode(pRExC_state, ANYOF, 0);
+
+    if (SIZE_ONLY) {
+       RExC_size += ANYOF_SKIP;
+       listsv = &PL_sv_undef; /* For code scanners: listsv always non-NULL. */
+    }
+    else {
+        ANYOF_FLAGS(ret) = 0;
+
+       RExC_emit += ANYOF_SKIP;
+       listsv = newSVpvs_flags("# comment\n", SVs_TEMP);
+       initial_listsv_len = SvCUR(listsv);
+        SvTEMP_off(listsv); /* Grr, TEMPs and mortals are conflated.  */
+    }
+
+    if (skip_white) {
+        RExC_parse = regpatws(pRExC_state, RExC_parse,
+                              FALSE /* means don't recognize comments */);
+    }
+
+    if (UCHARAT(RExC_parse) == '^') {  /* Complement of range. */
+       RExC_parse++;
+        invert = TRUE;
+        allow_multi_folds = FALSE;
+        RExC_naughty++;
+        if (skip_white) {
+            RExC_parse = regpatws(pRExC_state, RExC_parse,
+                                  FALSE /* means don't recognize comments */);
+        }
+    }
+
+    /* Check that they didn't say [:posix:] instead of [[:posix:]] */
+    if (!SIZE_ONLY && RExC_parse < RExC_end && POSIXCC(UCHARAT(RExC_parse))) {
+       const char *s = RExC_parse;
+       const char  c = *s++;
+
+       while (isWORDCHAR(*s))
+           s++;
+       if (*s && c == *s && s[1] == ']') {
+           SAVEFREESV(RExC_rx_sv);
+           ckWARN3reg(s+2,
+                      "POSIX syntax [%c %c] belongs inside character classes",
+                      c, c);
+           (void)ReREFCNT_inc(RExC_rx_sv);
+       }
+    }
+
+    /* If the caller wants us to just parse a single element, accomplish this
+     * by faking the loop ending condition */
+    if (stop_at_1 && RExC_end > RExC_parse) {
+        stop_ptr = RExC_parse + 1;
+    }
+
+    /* allow 1st char to be ']' (allowing it to be '-' is dealt with later) */
+    if (UCHARAT(RExC_parse) == ']')
+       goto charclassloop;
+
+parseit:
+    while (1) {
+        if  (RExC_parse >= stop_ptr) {
+            break;
+        }
+
+        if (skip_white) {
+            RExC_parse = regpatws(pRExC_state, RExC_parse,
+                                  FALSE /* means don't recognize comments */);
+        }
+
+        if  (UCHARAT(RExC_parse) == ']') {
+            break;
+        }
+
+    charclassloop:
+
+       namedclass = OOB_NAMEDCLASS; /* initialize as illegal */
+        save_value = value;
+        save_prevvalue = prevvalue;
+
+       if (!range) {
+           rangebegin = RExC_parse;
+           element_count++;
+       }
+       if (UTF) {
+           value = utf8n_to_uvchr((U8*)RExC_parse,
+                                  RExC_end - RExC_parse,
+                                  &numlen, UTF8_ALLOW_DEFAULT);
+           RExC_parse += numlen;
+       }
+       else
+           value = UCHARAT(RExC_parse++);
+
+        if (value == '['
+            && RExC_parse < RExC_end
+            && POSIXCC(UCHARAT(RExC_parse)))
+        {
+            namedclass = regpposixcc(pRExC_state, value, strict);
+        }
+        else if (value == '\\') {
+           if (UTF) {
+               value = utf8n_to_uvchr((U8*)RExC_parse,
+                                  RExC_end - RExC_parse,
+                                  &numlen, UTF8_ALLOW_DEFAULT);
+               RExC_parse += numlen;
+           }
+           else
+               value = UCHARAT(RExC_parse++);
+
+           /* Some compilers cannot handle switching on 64-bit integer
+            * values, therefore value cannot be an UV.  Yes, this will
+            * be a problem later if we want switch on Unicode.
+            * A similar issue a little bit later when switching on
+            * namedclass. --jhi */
+
+            /* If the \ is escaping white space when white space is being
+             * skipped, it means that that white space is wanted literally, and
+             * is already in 'value'.  Otherwise, need to translate the escape
+             * into what it signifies. */
+            if (! skip_white || ! is_PATWS_cp(value)) switch ((I32)value) {
+
+           case 'w':   namedclass = ANYOF_WORDCHAR;    break;
+           case 'W':   namedclass = ANYOF_NWORDCHAR;   break;
+           case 's':   namedclass = ANYOF_SPACE;       break;
+           case 'S':   namedclass = ANYOF_NSPACE;      break;
+           case 'd':   namedclass = ANYOF_DIGIT;       break;
+           case 'D':   namedclass = ANYOF_NDIGIT;      break;
+           case 'v':   namedclass = ANYOF_VERTWS;      break;
+           case 'V':   namedclass = ANYOF_NVERTWS;     break;
+           case 'h':   namedclass = ANYOF_HORIZWS;     break;
+           case 'H':   namedclass = ANYOF_NHORIZWS;    break;
+            case 'N':  /* Handle \N{NAME} in class */
+                {
+                    /* We only pay attention to the first char of
+                    multichar strings being returned. I kinda wonder
+                    if this makes sense as it does change the behaviour
+                    from earlier versions, OTOH that behaviour was broken
+                    as well. */
+                    if (! grok_bslash_N(pRExC_state, NULL, &value, flagp, depth,
+                                      TRUE, /* => charclass */
+                                      strict))
+                    {
+                        if (*flagp & RESTART_UTF8)
+                            FAIL("panic: grok_bslash_N set RESTART_UTF8");
+                        goto parseit;
+                    }
+                }
+                break;
+           case 'p':
+           case 'P':
+               {
+               char *e;
+
+                /* We will handle any undefined properties ourselves */
+                U8 swash_init_flags = _CORE_SWASH_INIT_RETURN_IF_UNDEF
+                                       /* And we actually would prefer to get
+                                        * the straight inversion list of the
+                                        * swash, since we will be accessing it
+                                        * anyway, to save a little time */
+                                      |_CORE_SWASH_INIT_ACCEPT_INVLIST;
+
+               if (RExC_parse >= RExC_end)
+                   vFAIL2("Empty \\%c{}", (U8)value);
+               if (*RExC_parse == '{') {
+                   const U8 c = (U8)value;
+                   e = strchr(RExC_parse++, '}');
+                    if (!e)
+                        vFAIL2("Missing right brace on \\%c{}", c);
+                   while (isSPACE(UCHARAT(RExC_parse)))
+                       RExC_parse++;
+                    if (e == RExC_parse)
+                        vFAIL2("Empty \\%c{}", c);
+                   n = e - RExC_parse;
+                   while (isSPACE(UCHARAT(RExC_parse + n - 1)))
+                       n--;
+               }
+               else {
+                   e = RExC_parse;
+                   n = 1;
+               }
+               if (!SIZE_ONLY) {
+                    SV* invlist;
+                    char* formatted;
+                    char* name;
+
+                   if (UCHARAT(RExC_parse) == '^') {
+                        RExC_parse++;
+                        n--;
+                         /* toggle.  (The rhs xor gets the single bit that
+                          * differs between P and p; the other xor inverts just
+                          * that bit) */
+                         value ^= 'P' ^ 'p';
+
+                        while (isSPACE(UCHARAT(RExC_parse))) {
+                             RExC_parse++;
+                             n--;
+                        }
+                   }
+                    /* Try to get the definition of the property into
+                     * <invlist>.  If /i is in effect, the effective property
+                     * will have its name be <__NAME_i>.  The design is
+                     * discussed in commit
+                     * 2f833f5208e26b208886e51e09e2c072b5eabb46 */
+                    formatted = Perl_form(aTHX_
+                                          "%s%.*s%s\n",
+                                          (FOLD) ? "__" : "",
+                                          (int)n,
+                                          RExC_parse,
+                                          (FOLD) ? "_i" : ""
+                                );
+                    name = savepvn(formatted, strlen(formatted));
+
+                    /* Look up the property name, and get its swash and
+                     * inversion list, if the property is found  */
+                    if (swash) {
+                        SvREFCNT_dec_NN(swash);
+                    }
+                    swash = _core_swash_init("utf8", name, &PL_sv_undef,
+                                             1, /* binary */
+                                             0, /* not tr/// */
+                                             NULL, /* No inversion list */
+                                             &swash_init_flags
+                                            );
+                    if (! swash || ! (invlist = _get_swash_invlist(swash))) {
+                        if (swash) {
+                            SvREFCNT_dec_NN(swash);
+                            swash = NULL;
+                        }
+
+                        /* Here didn't find it.  It could be a user-defined
+                         * property that will be available at run-time.  If we
+                         * accept only compile-time properties, is an error;
+                         * otherwise add it to the list for run-time look up */
+                        if (ret_invlist) {
+                            RExC_parse = e + 1;
+                            vFAIL2utf8f(
+                                "Property '%"UTF8f"' is unknown",
+                                UTF8fARG(UTF, n, name));
+                        }
+                        Perl_sv_catpvf(aTHX_ listsv, "%cutf8::%"UTF8f"\n",
+                                        (value == 'p' ? '+' : '!'),
+                                        UTF8fARG(UTF, n, name));
+                        has_user_defined_property = TRUE;
+
+                        /* We don't know yet, so have to assume that the
+                         * property could match something in the Latin1 range,
+                         * hence something that isn't utf8.  Note that this
+                         * would cause things in <depends_list> to match
+                         * inappropriately, except that any \p{}, including
+                         * this one forces Unicode semantics, which means there
+                         * is no <depends_list> */
+                        ANYOF_FLAGS(ret) |= ANYOF_NONBITMAP_NON_UTF8;
+                    }
+                    else {
+
+                        /* Here, did get the swash and its inversion list.  If
+                         * the swash is from a user-defined property, then this
+                         * whole character class should be regarded as such */
+                        if (swash_init_flags
+                            & _CORE_SWASH_INIT_USER_DEFINED_PROPERTY)
+                        {
+                            has_user_defined_property = TRUE;
+                        }
+                        else if
+                            /* We warn on matching an above-Unicode code point
+                             * if the match would return true, except don't
+                             * warn for \p{All}, which has exactly one element
+                             * = 0 */
+                            (_invlist_contains_cp(invlist, 0x110000)
+                                && (! (_invlist_len(invlist) == 1
+                                       && *invlist_array(invlist) == 0)))
+                        {
+                            warn_super = TRUE;
+                        }
+
+
+                        /* Invert if asking for the complement */
+                        if (value == 'P') {
+                           _invlist_union_complement_2nd(properties,
+                                                          invlist,
+                                                          &properties);
+
+                            /* The swash can't be used as-is, because we've
+                            * inverted things; delay removing it to here after
+                            * have copied its invlist above */
+                            SvREFCNT_dec_NN(swash);
+                            swash = NULL;
+                        }
+                        else {
+                            _invlist_union(properties, invlist, &properties);
+                       }
+                   }
+                   Safefree(name);
+               }
+               RExC_parse = e + 1;
+                namedclass = ANYOF_UNIPROP;  /* no official name, but it's
+                                                named */
+
+               /* \p means they want Unicode semantics */
+               RExC_uni_semantics = 1;
+               }
+               break;
+           case 'n':   value = '\n';                   break;
+           case 'r':   value = '\r';                   break;
+           case 't':   value = '\t';                   break;
+           case 'f':   value = '\f';                   break;
+           case 'b':   value = '\b';                   break;
+           case 'e':   value = ASCII_TO_NATIVE('\033');break;
+           case 'a':   value = '\a';                   break;
+           case 'o':
+               RExC_parse--;   /* function expects to be pointed at the 'o' */
+               {
+                   const char* error_msg;
+                   bool valid = grok_bslash_o(&RExC_parse,
+                                              &value,
+                                              &error_msg,
+                                               SIZE_ONLY,   /* warnings in pass
+                                                               1 only */
+                                               strict,
+                                               silence_non_portable,
+                                               UTF);
+                   if (! valid) {
+                       vFAIL(error_msg);
+                   }
+               }
+               if (PL_encoding && value < 0x100) {
+                   goto recode_encoding;
+               }
+               break;
+           case 'x':
+               RExC_parse--;   /* function expects to be pointed at the 'x' */
+               {
+                   const char* error_msg;
+                   bool valid = grok_bslash_x(&RExC_parse,
+                                              &value,
+                                              &error_msg,
+                                              TRUE, /* Output warnings */
+                                               strict,
+                                               silence_non_portable,
+                                               UTF);
+                    if (! valid) {
+                       vFAIL(error_msg);
+                   }
+               }
+               if (PL_encoding && value < 0x100)
+                   goto recode_encoding;
+               break;
+           case 'c':
+               value = grok_bslash_c(*RExC_parse++, SIZE_ONLY);
+               break;
+           case '0': case '1': case '2': case '3': case '4':
+           case '5': case '6': case '7':
+               {
+                   /* Take 1-3 octal digits */
+                   I32 flags = PERL_SCAN_SILENT_ILLDIGIT;
+                    numlen = (strict) ? 4 : 3;
+                    value = grok_oct(--RExC_parse, &numlen, &flags, NULL);
+                   RExC_parse += numlen;
+                    if (numlen != 3) {
+                        if (strict) {
+                            RExC_parse += (UTF) ? UTF8SKIP(RExC_parse) : 1;
+                            vFAIL("Need exactly 3 octal digits");
+                        }
+                        else if (! SIZE_ONLY /* like \08, \178 */
+                                 && numlen < 3
+                                 && RExC_parse < RExC_end
+                                 && isDIGIT(*RExC_parse)
+                                 && ckWARN(WARN_REGEXP))
+                        {
+                            SAVEFREESV(RExC_rx_sv);
+                            reg_warn_non_literal_string(
+                                 RExC_parse + 1,
+                                 form_short_octal_warning(RExC_parse, numlen));
+                            (void)ReREFCNT_inc(RExC_rx_sv);
+                        }
+                    }
+                   if (PL_encoding && value < 0x100)
+                       goto recode_encoding;
+                   break;
+               }
+           recode_encoding:
+               if (! RExC_override_recoding) {
+                   SV* enc = PL_encoding;
+                   value = reg_recode((const char)(U8)value, &enc);
+                   if (!enc) {
+                        if (strict) {
+                            vFAIL("Invalid escape in the specified encoding");
+                        }
+                        else if (SIZE_ONLY) {
+                            ckWARNreg(RExC_parse,
+                                 "Invalid escape in the specified encoding");
+                        }
+                    }
+                   break;
+               }
+           default:
+               /* Allow \_ to not give an error */
+               if (!SIZE_ONLY && isWORDCHAR(value) && value != '_') {
+                    if (strict) {
+                        vFAIL2("Unrecognized escape \\%c in character class",
+                               (int)value);
+                    }
+                    else {
+                        SAVEFREESV(RExC_rx_sv);
+                        ckWARN2reg(RExC_parse,
+                            "Unrecognized escape \\%c in character class passed through",
+                            (int)value);
+                        (void)ReREFCNT_inc(RExC_rx_sv);
+                    }
+               }
+               break;
+           }   /* End of switch on char following backslash */
+       } /* end of handling backslash escape sequences */
+#ifdef EBCDIC
+        else
+            literal_endpoint++;
+#endif
+
+        /* Here, we have the current token in 'value' */
+
+       if (namedclass > OOB_NAMEDCLASS) { /* this is a named class \blah */
+            U8 classnum;
+
+           /* a bad range like a-\d, a-[:digit:].  The '-' is taken as a
+            * literal, as is the character that began the false range, i.e.
+            * the 'a' in the examples */
+           if (range) {
+               if (!SIZE_ONLY) {
+                   const int w = (RExC_parse >= rangebegin)
+                                  ? RExC_parse - rangebegin
+                                  : 0;
+                    if (strict) {
+                        vFAIL2utf8f(
+                            "False [] range \"%"UTF8f"\"",
+                            UTF8fARG(UTF, w, rangebegin));
+                    }
+                    else {
+                        SAVEFREESV(RExC_rx_sv); /* in case of fatal warnings */
+                        ckWARN2reg(RExC_parse,
+                            "False [] range \"%"UTF8f"\"",
+                            UTF8fARG(UTF, w, rangebegin));
+                        (void)ReREFCNT_inc(RExC_rx_sv);
+                        cp_list = add_cp_to_invlist(cp_list, '-');
+                        cp_foldable_list = add_cp_to_invlist(cp_foldable_list,
+                                                             prevvalue);
+                    }
+               }
+
+               range = 0; /* this was not a true range */
+                element_count += 2; /* So counts for three values */
+           }
+
+            classnum = namedclass_to_classnum(namedclass);
+
+           if (LOC && namedclass < ANYOF_POSIXL_MAX
+#ifndef HAS_ISASCII
+                && classnum != _CC_ASCII
+#endif
+            ) {
+                /* What the Posix classes (like \w, [:space:]) match in locale
+                 * isn't knowable under locale until actual match time.  Room
+                 * must be reserved (one time per outer bracketed class) to
+                 * store such classes.  The space will contain a bit for each
+                 * named class that is to be matched against.  This isn't
+                 * needed for \p{} and pseudo-classes, as they are not affected
+                 * by locale, and hence are dealt with separately */
+                if (! need_class) {
+                    need_class = 1;
+                    if (SIZE_ONLY) {
+                        RExC_size += ANYOF_POSIXL_SKIP - ANYOF_SKIP;
+                    }
+                    else {
+                        RExC_emit += ANYOF_POSIXL_SKIP - ANYOF_SKIP;
+                    }
+                    ANYOF_FLAGS(ret) |= ANYOF_POSIXL;
+                    ANYOF_POSIXL_ZERO(ret);
+                }
+
+                /* See if it already matches the complement of this POSIX
+                 * class */
+                if ((ANYOF_FLAGS(ret) & ANYOF_POSIXL)
+                    && ANYOF_POSIXL_TEST(ret, namedclass + ((namedclass % 2)
+                                                            ? -1
+                                                            : 1)))
+                {
+                    posixl_matches_all = TRUE;
+                    break;  /* No need to continue.  Since it matches both
+                               e.g., \w and \W, it matches everything, and the
+                               bracketed class can be optimized into qr/./s */
+                }
+
+                /* Add this class to those that should be checked at runtime */
+                ANYOF_POSIXL_SET(ret, namedclass);
+
+                /* The above-Latin1 characters are not subject to locale rules.
+                 * Just add them, in the second pass, to the
+                 * unconditionally-matched list */
+                if (! SIZE_ONLY) {
+                    SV* scratch_list = NULL;
+
+                    /* Get the list of the above-Latin1 code points this
+                     * matches */
+                    _invlist_intersection_maybe_complement_2nd(PL_AboveLatin1,
+                                          PL_XPosix_ptrs[classnum],
+
+                                          /* Odd numbers are complements, like
+                                           * NDIGIT, NASCII, ... */
+                                          namedclass % 2 != 0,
+                                          &scratch_list);
+                    /* Checking if 'cp_list' is NULL first saves an extra
+                     * clone.  Its reference count will be decremented at the
+                     * next union, etc, or if this is the only instance, at the
+                     * end of the routine */
+                    if (! cp_list) {
+                        cp_list = scratch_list;
+                    }
+                    else {
+                        _invlist_union(cp_list, scratch_list, &cp_list);
+                        SvREFCNT_dec_NN(scratch_list);
+                    }
+                    continue;   /* Go get next character */
+                }
+            }
+            else if (! SIZE_ONLY) {
+
+                /* Here, not in pass1 (in that pass we skip calculating the
+                 * contents of this class), and is /l, or is a POSIX class for
+                 * which /l doesn't matter (or is a Unicode property, which is
+                 * skipped here). */
+                if (namedclass >= ANYOF_POSIXL_MAX) {  /* If a special class */
+                    if (namedclass != ANYOF_UNIPROP) { /* UNIPROP = \p and \P */
+
+                        /* Here, should be \h, \H, \v, or \V.  None of /d, /i
+                         * nor /l make a difference in what these match,
+                         * therefore we just add what they match to cp_list. */
+                        if (classnum != _CC_VERTSPACE) {
+                            assert(   namedclass == ANYOF_HORIZWS
+                                   || namedclass == ANYOF_NHORIZWS);
+
+                            /* It turns out that \h is just a synonym for
+                             * XPosixBlank */
+                            classnum = _CC_BLANK;
+                        }
+
+                        _invlist_union_maybe_complement_2nd(
+                                cp_list,
+                                PL_XPosix_ptrs[classnum],
+                                namedclass % 2 != 0,    /* Complement if odd
+                                                          (NHORIZWS, NVERTWS)
+                                                        */
+                                &cp_list);
+                    }
+                }
+                else {  /* Garden variety class.  If is NASCII, NDIGIT, ...
+                           complement and use nposixes */
+                    SV** posixes_ptr = namedclass % 2 == 0
+                                       ? &posixes
+                                       : &nposixes;
+                    SV** source_ptr = &PL_XPosix_ptrs[classnum];
+                    _invlist_union_maybe_complement_2nd(
+                                                     *posixes_ptr,
+                                                     *source_ptr,
+                                                     namedclass % 2 != 0,
+                                                     posixes_ptr);
+                }
+                continue;   /* Go get next character */
+           }
+       } /* end of namedclass \blah */
+
+        /* Here, we have a single value.  If 'range' is set, it is the ending
+         * of a range--check its validity.  Later, we will handle each
+         * individual code point in the range.  If 'range' isn't set, this
+         * could be the beginning of a range, so check for that by looking
+         * ahead to see if the next real character to be processed is the range
+         * indicator--the minus sign */
+
+        if (skip_white) {
+            RExC_parse = regpatws(pRExC_state, RExC_parse,
+                                FALSE /* means don't recognize comments */);
+        }
+
+       if (range) {
+           if (prevvalue > value) /* b-a */ {
+               const int w = RExC_parse - rangebegin;
+                vFAIL2utf8f(
+                    "Invalid [] range \"%"UTF8f"\"",
+                    UTF8fARG(UTF, w, rangebegin));
+               range = 0; /* not a valid range */
+           }
+       }
+       else {
+            prevvalue = value; /* save the beginning of the potential range */
+            if (! stop_at_1     /* Can't be a range if parsing just one thing */
+                && *RExC_parse == '-')
+            {
+                char* next_char_ptr = RExC_parse + 1;
+                if (skip_white) {   /* Get the next real char after the '-' */
+                    next_char_ptr = regpatws(pRExC_state,
+                                             RExC_parse + 1,
+                                             FALSE); /* means don't recognize
+                                                        comments */
+                }
+
+                /* If the '-' is at the end of the class (just before the ']',
+                 * it is a literal minus; otherwise it is a range */
+                if (next_char_ptr < RExC_end && *next_char_ptr != ']') {
+                    RExC_parse = next_char_ptr;
+
+                    /* a bad range like \w-, [:word:]- ? */
+                    if (namedclass > OOB_NAMEDCLASS) {
+                        if (strict || ckWARN(WARN_REGEXP)) {
+                            const int w =
+                                RExC_parse >= rangebegin ?
+                                RExC_parse - rangebegin : 0;
+                            if (strict) {
+                                vFAIL4("False [] range \"%*.*s\"",
+                                    w, w, rangebegin);
+                            }
+                            else {
+                                vWARN4(RExC_parse,
+                                    "False [] range \"%*.*s\"",
+                                    w, w, rangebegin);
+                            }
+                        }
+                        if (!SIZE_ONLY) {
+                            cp_list = add_cp_to_invlist(cp_list, '-');
+                        }
+                        element_count++;
+                    } else
+                        range = 1;     /* yeah, it's a range! */
+                    continue;  /* but do it the next time */
+                }
+           }
+       }
+
+        /* Here, <prevvalue> is the beginning of the range, if any; or <value>
+         * if not */
+
+       /* non-Latin1 code point implies unicode semantics.  Must be set in
+        * pass1 so is there for the whole of pass 2 */
+       if (value > 255) {
+           RExC_uni_semantics = 1;
+       }
+
+        /* Ready to process either the single value, or the completed range.
+         * For single-valued non-inverted ranges, we consider the possibility
+         * of multi-char folds.  (We made a conscious decision to not do this
+         * for the other cases because it can often lead to non-intuitive
+         * results.  For example, you have the peculiar case that:
+         *  "s s" =~ /^[^\xDF]+$/i => Y
+         *  "ss"  =~ /^[^\xDF]+$/i => N
+         *
+         * See [perl #89750] */
+        if (FOLD && allow_multi_folds && value == prevvalue) {
+            if (value == LATIN_SMALL_LETTER_SHARP_S
+                || (value > 255 && _invlist_contains_cp(PL_HasMultiCharFold,
+                                                        value)))
+            {
+                /* Here <value> is indeed a multi-char fold.  Get what it is */
+
+                U8 foldbuf[UTF8_MAXBYTES_CASE];
+                STRLEN foldlen;
+
+                UV folded = _to_uni_fold_flags(
+                                value,
+                                foldbuf,
+                                &foldlen,
+                                FOLD_FLAGS_FULL | (ASCII_FOLD_RESTRICTED
+                                                   ? FOLD_FLAGS_NOMIX_ASCII
+                                                   : 0)
+                                );
+
+                /* Here, <folded> should be the first character of the
+                 * multi-char fold of <value>, with <foldbuf> containing the
+                 * whole thing.  But, if this fold is not allowed (because of
+                 * the flags), <fold> will be the same as <value>, and should
+                 * be processed like any other character, so skip the special
+                 * handling */
+                if (folded != value) {
+
+                    /* Skip if we are recursed, currently parsing the class
+                     * again.  Otherwise add this character to the list of
+                     * multi-char folds. */
+                    if (! RExC_in_multi_char_class) {
+                        AV** this_array_ptr;
+                        AV* this_array;
+                        STRLEN cp_count = utf8_length(foldbuf,
+                                                      foldbuf + foldlen);
+                        SV* multi_fold = sv_2mortal(newSVpvn("", 0));
+
+                        Perl_sv_catpvf(aTHX_ multi_fold, "\\x{%"UVXf"}", value);
+
+
+                        if (! multi_char_matches) {
+                            multi_char_matches = newAV();
+                        }
+
+                        /* <multi_char_matches> is actually an array of arrays.
+                         * There will be one or two top-level elements: [2],
+                         * and/or [3].  The [2] element is an array, each
+                         * element thereof is a character which folds to TWO
+                         * characters; [3] is for folds to THREE characters.
+                         * (Unicode guarantees a maximum of 3 characters in any
+                         * fold.)  When we rewrite the character class below,
+                         * we will do so such that the longest folds are
+                         * written first, so that it prefers the longest
+                         * matching strings first.  This is done even if it
+                         * turns out that any quantifier is non-greedy, out of
+                         * programmer laziness.  Tom Christiansen has agreed
+                         * that this is ok.  This makes the test for the
+                         * ligature 'ffi' come before the test for 'ff' */
+                        if (av_exists(multi_char_matches, cp_count)) {
+                            this_array_ptr = (AV**) av_fetch(multi_char_matches,
+                                                             cp_count, FALSE);
+                            this_array = *this_array_ptr;
+                        }
+                        else {
+                            this_array = newAV();
+                            av_store(multi_char_matches, cp_count,
+                                     (SV*) this_array);
+                        }
+                        av_push(this_array, multi_fold);
+                    }
+
+                    /* This element should not be processed further in this
+                     * class */
+                    element_count--;
+                    value = save_value;
+                    prevvalue = save_prevvalue;
+                    continue;
+                }
+            }
+        }
+
+        /* Deal with this element of the class */
+       if (! SIZE_ONLY) {
+#ifndef EBCDIC
+            cp_foldable_list = _add_range_to_invlist(cp_foldable_list,
+                                                     prevvalue, value);
+#else
+            SV* this_range = _new_invlist(1);
+            _append_range_to_invlist(this_range, prevvalue, value);
+
+            /* In EBCDIC, the ranges 'A-Z' and 'a-z' are each not contiguous.
+             * If this range was specified using something like 'i-j', we want
+             * to include only the 'i' and the 'j', and not anything in
+             * between, so exclude non-ASCII, non-alphabetics from it.
+             * However, if the range was specified with something like
+             * [\x89-\x91] or [\x89-j], all code points within it should be
+             * included.  literal_endpoint==2 means both ends of the range used
+             * a literal character, not \x{foo} */
+           if (literal_endpoint == 2
+                && ((prevvalue >= 'a' && value <= 'z')
+                    || (prevvalue >= 'A' && value <= 'Z')))
+            {
+                _invlist_intersection(this_range, PL_ASCII,
+                                      &this_range);
+
+                /* Since this above only contains ascii, the intersection of it
+                 * with anything will still yield only ascii */
+                _invlist_intersection(this_range, PL_XPosix_ptrs[_CC_ALPHA],
+                                      &this_range);
+            }
+            _invlist_union(cp_foldable_list, this_range, &cp_foldable_list);
+            literal_endpoint = 0;
+#endif
+        }
+
+       range = 0; /* this range (if it was one) is done now */
+    } /* End of loop through all the text within the brackets */
+
+    /* If anything in the class expands to more than one character, we have to
+     * deal with them by building up a substitute parse string, and recursively
+     * calling reg() on it, instead of proceeding */
+    if (multi_char_matches) {
+       SV * substitute_parse = newSVpvn_flags("?:", 2, SVs_TEMP);
+        I32 cp_count;
+       STRLEN len;
+       char *save_end = RExC_end;
+       char *save_parse = RExC_parse;
+        bool first_time = TRUE;     /* First multi-char occurrence doesn't get
+                                       a "|" */
+        I32 reg_flags;
+
+        assert(! invert);
+#if 0   /* Have decided not to deal with multi-char folds in inverted classes,
+           because too confusing */
+        if (invert) {
+            sv_catpv(substitute_parse, "(?:");
+        }
+#endif
+
+        /* Look at the longest folds first */
+        for (cp_count = av_tindex(multi_char_matches); cp_count > 0; cp_count--) {
+
+            if (av_exists(multi_char_matches, cp_count)) {
+                AV** this_array_ptr;
+                SV* this_sequence;
+
+                this_array_ptr = (AV**) av_fetch(multi_char_matches,
+                                                 cp_count, FALSE);
+                while ((this_sequence = av_pop(*this_array_ptr)) !=
+                                                                &PL_sv_undef)
+                {
+                    if (! first_time) {
+                        sv_catpv(substitute_parse, "|");
+                    }
+                    first_time = FALSE;
+
+                    sv_catpv(substitute_parse, SvPVX(this_sequence));
+                }
+            }
+        }
+
+        /* If the character class contains anything else besides these
+         * multi-character folds, have to include it in recursive parsing */
+        if (element_count) {
+            sv_catpv(substitute_parse, "|[");
+            sv_catpvn(substitute_parse, orig_parse, RExC_parse - orig_parse);
+            sv_catpv(substitute_parse, "]");
+        }
+
+        sv_catpv(substitute_parse, ")");
+#if 0
+        if (invert) {
+            /* This is a way to get the parse to skip forward a whole named
+             * sequence instead of matching the 2nd character when it fails the
+             * first */
+            sv_catpv(substitute_parse, "(*THEN)(*SKIP)(*FAIL)|.)");
+        }
+#endif
+
+       RExC_parse = SvPV(substitute_parse, len);
+       RExC_end = RExC_parse + len;
+        RExC_in_multi_char_class = 1;
+        RExC_emit = (regnode *)orig_emit;
+
+       ret = reg(pRExC_state, 1, &reg_flags, depth+1);
+
+       *flagp |= reg_flags&(HASWIDTH|SIMPLE|SPSTART|POSTPONED|RESTART_UTF8);
+
+       RExC_parse = save_parse;
+       RExC_end = save_end;
+       RExC_in_multi_char_class = 0;
+        SvREFCNT_dec_NN(multi_char_matches);
+        return ret;
+    }
+
+    /* Here, we've gone through the entire class and dealt with multi-char
+     * folds.  We are now in a position that we can do some checks to see if we
+     * can optimize this ANYOF node into a simpler one, even in Pass 1.
+     * Currently we only do two checks:
+     * 1) is in the unlikely event that the user has specified both, eg. \w and
+     *    \W under /l, then the class matches everything.  (This optimization
+     *    is done only to make the optimizer code run later work.)
+     * 2) if the character class contains only a single element (including a
+     *    single range), we see if there is an equivalent node for it.
+     * Other checks are possible */
+    if (! ret_invlist   /* Can't optimize if returning the constructed
+                           inversion list */
+        && (UNLIKELY(posixl_matches_all) || element_count == 1))
+    {
+        U8 op = END;
+        U8 arg = 0;
+
+        if (UNLIKELY(posixl_matches_all)) {
+            op = SANY;
+        }
+        else if (namedclass > OOB_NAMEDCLASS) { /* this is a named class, like
+                                                   \w or [:digit:] or \p{foo}
+                                                 */
+
+            /* All named classes are mapped into POSIXish nodes, with its FLAG
+             * argument giving which class it is */
+            switch ((I32)namedclass) {
+                case ANYOF_UNIPROP:
+                    break;
+
+                /* These don't depend on the charset modifiers.  They always
+                 * match under /u rules */
+                case ANYOF_NHORIZWS:
+                case ANYOF_HORIZWS:
+                    namedclass = ANYOF_BLANK + namedclass - ANYOF_HORIZWS;
+                    /* FALLTHROUGH */
+
+                case ANYOF_NVERTWS:
+                case ANYOF_VERTWS:
+                    op = POSIXU;
+                    goto join_posix;
+
+                /* The actual POSIXish node for all the rest depends on the
+                 * charset modifier.  The ones in the first set depend only on
+                 * ASCII or, if available on this platform, locale */
+                case ANYOF_ASCII:
+                case ANYOF_NASCII:
+#ifdef HAS_ISASCII
+                    op = (LOC) ? POSIXL : POSIXA;
+#else
+                    op = POSIXA;
+#endif
+                    goto join_posix;
+
+                case ANYOF_NCASED:
+                case ANYOF_LOWER:
+                case ANYOF_NLOWER:
+                case ANYOF_UPPER:
+                case ANYOF_NUPPER:
+                    /* under /a could be alpha */
+                    if (FOLD) {
+                        if (ASCII_RESTRICTED) {
+                            namedclass = ANYOF_ALPHA + (namedclass % 2);
+                        }
+                        else if (! LOC) {
+                            break;
+                        }
+                    }
+                    /* FALLTHROUGH */
+
+                /* The rest have more possibilities depending on the charset.
+                 * We take advantage of the enum ordering of the charset
+                 * modifiers to get the exact node type, */
+                default:
+                    op = POSIXD + get_regex_charset(RExC_flags);
+                    if (op > POSIXA) { /* /aa is same as /a */
+                        op = POSIXA;
+                    }
+
+                join_posix:
+                    /* The odd numbered ones are the complements of the
+                     * next-lower even number one */
+                    if (namedclass % 2 == 1) {
+                        invert = ! invert;
+                        namedclass--;
+                    }
+                    arg = namedclass_to_classnum(namedclass);
+                    break;
+            }
+        }
+        else if (value == prevvalue) {
+
+            /* Here, the class consists of just a single code point */
+
+            if (invert) {
+                if (! LOC && value == '\n') {
+                    op = REG_ANY; /* Optimize [^\n] */
+                    *flagp |= HASWIDTH|SIMPLE;
+                    RExC_naughty++;
+                }
+            }
+            else if (value < 256 || UTF) {
+
+                /* Optimize a single value into an EXACTish node, but not if it
+                 * would require converting the pattern to UTF-8. */
+                op = compute_EXACTish(pRExC_state);
+            }
+        } /* Otherwise is a range */
+        else if (! LOC) {   /* locale could vary these */
+            if (prevvalue == '0') {
+                if (value == '9') {
+                    arg = _CC_DIGIT;
+                    op = POSIXA;
+                }
+            }
+        }
+
+        /* Here, we have changed <op> away from its initial value iff we found
+         * an optimization */
+        if (op != END) {
+
+            /* Throw away this ANYOF regnode, and emit the calculated one,
+             * which should correspond to the beginning, not current, state of
+             * the parse */
+            const char * cur_parse = RExC_parse;
+            RExC_parse = (char *)orig_parse;
+            if ( SIZE_ONLY) {
+                if (! LOC) {
+
+                    /* To get locale nodes to not use the full ANYOF size would
+                     * require moving the code above that writes the portions
+                     * of it that aren't in other nodes to after this point.
+                     * e.g.  ANYOF_POSIXL_SET */
+                    RExC_size = orig_size;
+                }
+            }
+            else {
+                RExC_emit = (regnode *)orig_emit;
+                if (PL_regkind[op] == POSIXD) {
+                    if (op == POSIXL) {
+                        RExC_contains_locale = 1;
+                    }
+                    if (invert) {
+                        op += NPOSIXD - POSIXD;
+                    }
+                }
+            }
+
+            ret = reg_node(pRExC_state, op);
+
+            if (PL_regkind[op] == POSIXD || PL_regkind[op] == NPOSIXD) {
+                if (! SIZE_ONLY) {
+                    FLAGS(ret) = arg;
+                }
+                *flagp |= HASWIDTH|SIMPLE;
+            }
+            else if (PL_regkind[op] == EXACT) {
+                alloc_maybe_populate_EXACT(pRExC_state, ret, flagp, 0, value,
+                                           TRUE /* downgradable to EXACT */
+                                           );
+            }
+
+            RExC_parse = (char *) cur_parse;
+
+            SvREFCNT_dec(posixes);
+            SvREFCNT_dec(nposixes);
+            SvREFCNT_dec(cp_list);
+            SvREFCNT_dec(cp_foldable_list);
+            return ret;
+        }
+    }
+
+    if (SIZE_ONLY)
+        return ret;
+    /****** !SIZE_ONLY (Pass 2) AFTER HERE *********/
+
+    /* If folding, we calculate all characters that could fold to or from the
+     * ones already on the list */
+    if (cp_foldable_list) {
+        if (FOLD) {
+            UV start, end;     /* End points of code point ranges */
+
+            SV* fold_intersection = NULL;
+            SV** use_list;
+
+            /* Our calculated list will be for Unicode rules.  For locale
+             * matching, we have to keep a separate list that is consulted at
+             * runtime only when the locale indicates Unicode rules.  For
+             * non-locale, we just use to the general list */
+            if (LOC) {
+                use_list = &only_utf8_locale_list;
+            }
+            else {
+                use_list = &cp_list;
+            }
+
+            /* Only the characters in this class that participate in folds need
+             * be checked.  Get the intersection of this class and all the
+             * possible characters that are foldable.  This can quickly narrow
+             * down a large class */
+            _invlist_intersection(PL_utf8_foldable, cp_foldable_list,
+                                  &fold_intersection);
+
+            /* The folds for all the Latin1 characters are hard-coded into this
+             * program, but we have to go out to disk to get the others. */
+            if (invlist_highest(cp_foldable_list) >= 256) {
+
+                /* This is a hash that for a particular fold gives all
+                 * characters that are involved in it */
+                if (! PL_utf8_foldclosures) {
+
+                    /* If the folds haven't been read in, call a fold function
+                     * to force that */
+                    if (! PL_utf8_tofold) {
+                        U8 dummy[UTF8_MAXBYTES_CASE+1];
+
+                        /* This string is just a short named one above \xff */
+                        to_utf8_fold((U8*) HYPHEN_UTF8, dummy, NULL);
+                        assert(PL_utf8_tofold); /* Verify that worked */
+                    }
+                    PL_utf8_foldclosures
+                                      = _swash_inversion_hash(PL_utf8_tofold);
+                }
+            }
+
+            /* Now look at the foldable characters in this class individually */
+            invlist_iterinit(fold_intersection);
+            while (invlist_iternext(fold_intersection, &start, &end)) {
+                UV j;
+
+                /* Look at every character in the range */
+                for (j = start; j <= end; j++) {
+                    U8 foldbuf[UTF8_MAXBYTES_CASE+1];
+                    STRLEN foldlen;
+                    SV** listp;
+
+                    if (j < 256) {
+
+                        /* We have the latin1 folding rules hard-coded here so
+                         * that an innocent-looking character class, like
+                         * /[ks]/i won't have to go out to disk to find the
+                         * possible matches.  XXX It would be better to
+                         * generate these via regen, in case a new version of
+                         * the Unicode standard adds new mappings, though that
+                         * is not really likely, and may be caught by the
+                         * default: case of the switch below. */
+
+                        if (IS_IN_SOME_FOLD_L1(j)) {
+
+                            /* ASCII is always matched; non-ASCII is matched
+                             * only under Unicode rules (which could happen
+                             * under /l if the locale is a UTF-8 one */
+                            if (isASCII(j) || ! DEPENDS_SEMANTICS) {
+                                *use_list = add_cp_to_invlist(*use_list,
+                                                            PL_fold_latin1[j]);
+                            }
+                            else {
+                                depends_list =
+                                 add_cp_to_invlist(depends_list,
+                                                   PL_fold_latin1[j]);
+                            }
+                        }
+
+                        if (HAS_NONLATIN1_FOLD_CLOSURE(j)
+                            && (! isASCII(j) || ! ASCII_FOLD_RESTRICTED))
+                        {
+                            /* Certain Latin1 characters have matches outside
+                            * Latin1.  To get here, <j> is one of those
+                            * characters.   None of these matches is valid for
+                            * ASCII characters under /aa, which is why the 'if'
+                            * just above excludes those.  These matches only
+                            * happen when the target string is utf8.  The code
+                            * below adds the single fold closures for <j> to the
+                            * inversion list. */
+
+                            switch (j) {
+                                case 'k':
+                                case 'K':
+                                  *use_list =
+                                     add_cp_to_invlist(*use_list, KELVIN_SIGN);
+                                    break;
+                                case 's':
+                                case 'S':
+                                  *use_list = add_cp_to_invlist(*use_list,
+                                                    LATIN_SMALL_LETTER_LONG_S);
+                                    break;
+                                case MICRO_SIGN:
+                                  *use_list = add_cp_to_invlist(*use_list,
+                                                      GREEK_CAPITAL_LETTER_MU);
+                                  *use_list = add_cp_to_invlist(*use_list,
+                                                        GREEK_SMALL_LETTER_MU);
+                                    break;
+                                case LATIN_CAPITAL_LETTER_A_WITH_RING_ABOVE:
+                                case LATIN_SMALL_LETTER_A_WITH_RING_ABOVE:
+                                  *use_list =
+                                   add_cp_to_invlist(*use_list, ANGSTROM_SIGN);
+                                    break;
+                                case LATIN_SMALL_LETTER_Y_WITH_DIAERESIS:
+                                  *use_list = add_cp_to_invlist(*use_list,
+                                        LATIN_CAPITAL_LETTER_Y_WITH_DIAERESIS);
+                                    break;
+                                case LATIN_SMALL_LETTER_SHARP_S:
+                                  *use_list = add_cp_to_invlist(*use_list,
+                                                 LATIN_CAPITAL_LETTER_SHARP_S);
+                                    break;
+                                case 'F': case 'f':
+                                case 'I': case 'i':
+                                case 'L': case 'l':
+                                case 'T': case 't':
+                                case 'A': case 'a':
+                                case 'H': case 'h':
+                                case 'J': case 'j':
+                                case 'N': case 'n':
+                                case 'W': case 'w':
+                                case 'Y': case 'y':
+                                    /* These all are targets of multi-character
+                                     * folds from code points that require UTF8
+                                     * to express, so they can't match unless
+                                     * the target string is in UTF-8, so no
+                                     * action here is necessary, as regexec.c
+                                     * properly handles the general case for
+                                     * UTF-8 matching and multi-char folds */
+                                    break;
+                                default:
+                                    /* Use deprecated warning to increase the
+                                    * chances of this being output */
+                                    ckWARN2reg_d(RExC_parse, "Perl folding rules are not up-to-date for 0x%"UVXf"; please use the perlbug utility to report;", j);
+                                    break;
+                            }
+                        }
+                        continue;
+                    }
+
+                    /* Here is an above Latin1 character.  We don't have the
+                     * rules hard-coded for it.  First, get its fold.  This is
+                     * the simple fold, as the multi-character folds have been
+                     * handled earlier and separated out */
+                    _to_uni_fold_flags(j, foldbuf, &foldlen,
+                                                        (ASCII_FOLD_RESTRICTED)
+                                                        ? FOLD_FLAGS_NOMIX_ASCII
+                                                        : 0);
+
+                    /* Single character fold of above Latin1.  Add everything in
+                    * its fold closure to the list that this node should match.
+                    * The fold closures data structure is a hash with the keys
+                    * being the UTF-8 of every character that is folded to, like
+                    * 'k', and the values each an array of all code points that
+                    * fold to its key.  e.g. [ 'k', 'K', KELVIN_SIGN ].
+                    * Multi-character folds are not included */
+                    if ((listp = hv_fetch(PL_utf8_foldclosures,
+                                        (char *) foldbuf, foldlen, FALSE)))
+                    {
+                        AV* list = (AV*) *listp;
+                        IV k;
+                        for (k = 0; k <= av_tindex(list); k++) {
+                            SV** c_p = av_fetch(list, k, FALSE);
+                            UV c;
+                            if (c_p == NULL) {
+                                Perl_croak(aTHX_ "panic: invalid PL_utf8_foldclosures structure");
+                            }
+                            c = SvUV(*c_p);
+
+                            /* /aa doesn't allow folds between ASCII and non- */
+                            if ((ASCII_FOLD_RESTRICTED
+                                && (isASCII(c) != isASCII(j))))
+                            {
+                                continue;
+                            }
+
+                            /* Folds under /l which cross the 255/256 boundary
+                             * are added to a separate list.  (These are valid
+                             * only when the locale is UTF-8.) */
+                            if (c < 256 && LOC) {
+                                *use_list = add_cp_to_invlist(*use_list, c);
+                                continue;
+                            }
+
+                            if (isASCII(c) || c > 255 || AT_LEAST_UNI_SEMANTICS)
+                            {
+                                cp_list = add_cp_to_invlist(cp_list, c);
+                            }
+                            else {
+                                /* Similarly folds involving non-ascii Latin1
+                                * characters under /d are added to their list */
+                                depends_list = add_cp_to_invlist(depends_list,
+                                                                 c);
+                            }
+                        }
+                    }
+                }
+            }
+            SvREFCNT_dec_NN(fold_intersection);
+        }
+
+        /* Now that we have finished adding all the folds, there is no reason
+         * to keep the foldable list separate */
+        _invlist_union(cp_list, cp_foldable_list, &cp_list);
+       SvREFCNT_dec_NN(cp_foldable_list);
+    }
+
+    /* And combine the result (if any) with any inversion list from posix
+     * classes.  The lists are kept separate up to now because we don't want to
+     * fold the classes (folding of those is automatically handled by the swash
+     * fetching code) */
+    if (posixes || nposixes) {
+        if (posixes && AT_LEAST_ASCII_RESTRICTED) {
+            /* Under /a and /aa, nothing above ASCII matches these */
+            _invlist_intersection(posixes,
+                                  PL_XPosix_ptrs[_CC_ASCII],
+                                  &posixes);
+        }
+        if (nposixes) {
+            if (DEPENDS_SEMANTICS) {
+                /* Under /d, everything in the upper half of the Latin1 range
+                 * matches these complements */
+                ANYOF_FLAGS(ret) |= ANYOF_NON_UTF8_NON_ASCII_ALL;
+            }
+            else if (AT_LEAST_ASCII_RESTRICTED) {
+                /* Under /a and /aa, everything above ASCII matches these
+                 * complements */
+                _invlist_union_complement_2nd(nposixes,
+                                              PL_XPosix_ptrs[_CC_ASCII],
+                                              &nposixes);
+            }
+            if (posixes) {
+                _invlist_union(posixes, nposixes, &posixes);
+                SvREFCNT_dec_NN(nposixes);
+            }
+            else {
+                posixes = nposixes;
+            }
+        }
+        if (! DEPENDS_SEMANTICS) {
+            if (cp_list) {
+                _invlist_union(cp_list, posixes, &cp_list);
+                SvREFCNT_dec_NN(posixes);
+            }
+            else {
+                cp_list = posixes;
+            }
+        }
+        else {
+            /* Under /d, we put into a separate list the Latin1 things that
+             * match only when the target string is utf8 */
+            SV* nonascii_but_latin1_properties = NULL;
+            _invlist_intersection(posixes, PL_UpperLatin1,
+                                  &nonascii_but_latin1_properties);
+            _invlist_subtract(posixes, nonascii_but_latin1_properties,
+                              &posixes);
+            if (cp_list) {
+                _invlist_union(cp_list, posixes, &cp_list);
+                SvREFCNT_dec_NN(posixes);
+            }
+            else {
+                cp_list = posixes;
+            }
+
+            if (depends_list) {
+                _invlist_union(depends_list, nonascii_but_latin1_properties,
+                               &depends_list);
+                SvREFCNT_dec_NN(nonascii_but_latin1_properties);
+            }
+            else {
+                depends_list = nonascii_but_latin1_properties;
+            }
+        }
+    }
+
+    /* And combine the result (if any) with any inversion list from properties.
+     * The lists are kept separate up to now so that we can distinguish the two
+     * in regards to matching above-Unicode.  A run-time warning is generated
+     * if a Unicode property is matched against a non-Unicode code point. But,
+     * we allow user-defined properties to match anything, without any warning,
+     * and we also suppress the warning if there is a portion of the character
+     * class that isn't a Unicode property, and which matches above Unicode, \W
+     * or [\x{110000}] for example.
+     * (Note that in this case, unlike the Posix one above, there is no
+     * <depends_list>, because having a Unicode property forces Unicode
+     * semantics */
+    if (properties) {
+        if (cp_list) {
+
+            /* If it matters to the final outcome, see if a non-property
+             * component of the class matches above Unicode.  If so, the
+             * warning gets suppressed.  This is true even if just a single
+             * such code point is specified, as though not strictly correct if
+             * another such code point is matched against, the fact that they
+             * are using above-Unicode code points indicates they should know
+             * the issues involved */
+            if (warn_super) {
+                warn_super = ! (invert
+                               ^ (invlist_highest(cp_list) > PERL_UNICODE_MAX));
+            }
+
+            _invlist_union(properties, cp_list, &cp_list);
+            SvREFCNT_dec_NN(properties);
+        }
+        else {
+            cp_list = properties;
+        }
+
+        if (warn_super) {
+            ANYOF_FLAGS(ret) |= ANYOF_WARN_SUPER;
+        }
+    }
+
+    /* Here, we have calculated what code points should be in the character
+     * class.
+     *
+     * Now we can see about various optimizations.  Fold calculation (which we
+     * did above) needs to take place before inversion.  Otherwise /[^k]/i
+     * would invert to include K, which under /i would match k, which it
+     * shouldn't.  Therefore we can't invert folded locale now, as it won't be
+     * folded until runtime */
+
+    /* If we didn't do folding, it's because some information isn't available
+     * until runtime; set the run-time fold flag for these.  (We don't have to
+     * worry about properties folding, as that is taken care of by the swash
+     * fetching).  We know to set the flag if we have a non-NULL list for UTF-8
+     * locales, or the class matches at least one 0-255 range code point */
+    if (LOC && FOLD) {
+        if (only_utf8_locale_list) {
+            ANYOF_FLAGS(ret) |= ANYOF_LOC_FOLD;
+        }
+        else if (cp_list) { /* Look to see if there a 0-255 code point is in
+                               the list */
+            UV start, end;
+            invlist_iterinit(cp_list);
+            if (invlist_iternext(cp_list, &start, &end) && start < 256) {
+                ANYOF_FLAGS(ret) |= ANYOF_LOC_FOLD;
+            }
+            invlist_iterfinish(cp_list);
+        }
+    }
+
+    /* Optimize inverted simple patterns (e.g. [^a-z]) when everything is known
+     * at compile time.  Besides not inverting folded locale now, we can't
+     * invert if there are things such as \w, which aren't known until runtime
+     * */
+    if (cp_list
+        && invert
+        && ! (ANYOF_FLAGS(ret) & (ANYOF_LOCALE_FLAGS))
+       && ! depends_list
+       && ! HAS_NONLOCALE_RUNTIME_PROPERTY_DEFINITION)
+    {
+        _invlist_invert(cp_list);
+
+        /* Any swash can't be used as-is, because we've inverted things */
+        if (swash) {
+            SvREFCNT_dec_NN(swash);
+            swash = NULL;
+        }
+
+       /* Clear the invert flag since have just done it here */
+       invert = FALSE;
+    }
+
+    if (ret_invlist) {
+        *ret_invlist = cp_list;
+        SvREFCNT_dec(swash);
+
+        /* Discard the generated node */
+        if (SIZE_ONLY) {
+            RExC_size = orig_size;
+        }
+        else {
+            RExC_emit = orig_emit;
+        }
+        return orig_emit;
+    }
+
+    /* Some character classes are equivalent to other nodes.  Such nodes take
+     * up less room and generally fewer operations to execute than ANYOF nodes.
+     * Above, we checked for and optimized into some such equivalents for
+     * certain common classes that are easy to test.  Getting to this point in
+     * the code means that the class didn't get optimized there.  Since this
+     * code is only executed in Pass 2, it is too late to save space--it has
+     * been allocated in Pass 1, and currently isn't given back.  But turning
+     * things into an EXACTish node can allow the optimizer to join it to any
+     * adjacent such nodes.  And if the class is equivalent to things like /./,
+     * expensive run-time swashes can be avoided.  Now that we have more
+     * complete information, we can find things necessarily missed by the
+     * earlier code.  I (khw) am not sure how much to look for here.  It would
+     * be easy, but perhaps too slow, to check any candidates against all the
+     * node types they could possibly match using _invlistEQ(). */
+
+    if (cp_list
+        && ! invert
+        && ! depends_list
+        && ! (ANYOF_FLAGS(ret) & (ANYOF_LOCALE_FLAGS))
+        && ! HAS_NONLOCALE_RUNTIME_PROPERTY_DEFINITION
+
+           /* We don't optimize if we are supposed to make sure all non-Unicode
+            * code points raise a warning, as only ANYOF nodes have this check.
+            * */
+        && ! ((ANYOF_FLAGS(ret) | ANYOF_WARN_SUPER) && ALWAYS_WARN_SUPER))
+    {
+        UV start, end;
+        U8 op = END;  /* The optimzation node-type */
+        const char * cur_parse= RExC_parse;
+
+        invlist_iterinit(cp_list);
+        if (! invlist_iternext(cp_list, &start, &end)) {
+
+            /* Here, the list is empty.  This happens, for example, when a
+             * Unicode property is the only thing in the character class, and
+             * it doesn't match anything.  (perluniprops.pod notes such
+             * properties) */
+            op = OPFAIL;
+            *flagp |= HASWIDTH|SIMPLE;
+        }
+        else if (start == end) {    /* The range is a single code point */
+            if (! invlist_iternext(cp_list, &start, &end)
+
+                    /* Don't do this optimization if it would require changing
+                     * the pattern to UTF-8 */
+                && (start < 256 || UTF))
+            {
+                /* Here, the list contains a single code point.  Can optimize
+                 * into an EXACTish node */
+
+                value = start;
+
+                if (! FOLD) {
+                    op = EXACT;
+                }
+                else if (LOC) {
+
+                    /* A locale node under folding with one code point can be
+                     * an EXACTFL, as its fold won't be calculated until
+                     * runtime */
+                    op = EXACTFL;
+                }
+                else {
+
+                    /* Here, we are generally folding, but there is only one
+                     * code point to match.  If we have to, we use an EXACT
+                     * node, but it would be better for joining with adjacent
+                     * nodes in the optimization pass if we used the same
+                     * EXACTFish node that any such are likely to be.  We can
+                     * do this iff the code point doesn't participate in any
+                     * folds.  For example, an EXACTF of a colon is the same as
+                     * an EXACT one, since nothing folds to or from a colon. */
+                    if (value < 256) {
+                        if (IS_IN_SOME_FOLD_L1(value)) {
+                            op = EXACT;
+                        }
+                    }
+                    else {
+                        if (_invlist_contains_cp(PL_utf8_foldable, value)) {
+                            op = EXACT;
+                        }
+                    }
+
+                    /* If we haven't found the node type, above, it means we
+                     * can use the prevailing one */
+                    if (op == END) {
+                        op = compute_EXACTish(pRExC_state);
+                    }
+                }
+            }
+        }
+        else if (start == 0) {
+            if (end == UV_MAX) {
+                op = SANY;
+                *flagp |= HASWIDTH|SIMPLE;
+                RExC_naughty++;
+            }
+            else if (end == '\n' - 1
+                    && invlist_iternext(cp_list, &start, &end)
+                    && start == '\n' + 1 && end == UV_MAX)
+            {
+                op = REG_ANY;
+                *flagp |= HASWIDTH|SIMPLE;
+                RExC_naughty++;
+            }
+        }
+        invlist_iterfinish(cp_list);
+
+        if (op != END) {
+            RExC_parse = (char *)orig_parse;
+            RExC_emit = (regnode *)orig_emit;
+
+            ret = reg_node(pRExC_state, op);
+
+            RExC_parse = (char *)cur_parse;
+
+            if (PL_regkind[op] == EXACT) {
+                alloc_maybe_populate_EXACT(pRExC_state, ret, flagp, 0, value,
+                                           TRUE /* downgradable to EXACT */
+                                          );
+            }
+
+            SvREFCNT_dec_NN(cp_list);
+            return ret;
+        }
+    }
+
+    /* Here, <cp_list> contains all the code points we can determine at
+     * compile time that match under all conditions.  Go through it, and
+     * for things that belong in the bitmap, put them there, and delete from
+     * <cp_list>.  While we are at it, see if everything above 255 is in the
+     * list, and if so, set a flag to speed up execution */
+
+    populate_ANYOF_from_invlist(ret, &cp_list);
+
+    if (invert) {
+        ANYOF_FLAGS(ret) |= ANYOF_INVERT;
+    }
+
+    /* Here, the bitmap has been populated with all the Latin1 code points that
+     * always match.  Can now add to the overall list those that match only
+     * when the target string is UTF-8 (<depends_list>). */
+    if (depends_list) {
+       if (cp_list) {
+           _invlist_union(cp_list, depends_list, &cp_list);
+           SvREFCNT_dec_NN(depends_list);
+       }
+       else {
+           cp_list = depends_list;
+       }
+        ANYOF_FLAGS(ret) |= ANYOF_UTF8;
+    }
+
+    /* If there is a swash and more than one element, we can't use the swash in
+     * the optimization below. */
+    if (swash && element_count > 1) {
+       SvREFCNT_dec_NN(swash);
+       swash = NULL;
+    }
+
+    set_ANYOF_arg(pRExC_state, ret, cp_list,
+                  (HAS_NONLOCALE_RUNTIME_PROPERTY_DEFINITION)
+                   ? listsv : NULL,
+                  only_utf8_locale_list,
+                  swash, has_user_defined_property);
+
+    *flagp |= HASWIDTH|SIMPLE;
+
+    if (ANYOF_FLAGS(ret) & ANYOF_LOCALE_FLAGS) {
+        RExC_contains_locale = 1;
+    }
+
+    return ret;
+}
+
+#undef HAS_NONLOCALE_RUNTIME_PROPERTY_DEFINITION
+
+STATIC void
+S_set_ANYOF_arg(pTHX_ RExC_state_t* const pRExC_state,
+                regnode* const node,
+                SV* const cp_list,
+                SV* const runtime_defns,
+                SV* const only_utf8_locale_list,
+                SV* const swash,
+                const bool has_user_defined_property)
+{
+    /* Sets the arg field of an ANYOF-type node 'node', using information about
+     * the node passed-in.  If there is nothing outside the node's bitmap, the
+     * arg is set to ANYOF_NONBITMAP_EMPTY.  Otherwise, it sets the argument to
+     * the count returned by add_data(), having allocated and stored an array,
+     * av, that that count references, as follows:
+     *  av[0] stores the character class description in its textual form.
+     *        This is used later (regexec.c:Perl_regclass_swash()) to
+     *        initialize the appropriate swash, and is also useful for dumping
+     *        the regnode.  This is set to &PL_sv_undef if the textual
+     *        description is not needed at run-time (as happens if the other
+     *        elements completely define the class)
+     *  av[1] if &PL_sv_undef, is a placeholder to later contain the swash
+     *        computed from av[0].  But if no further computation need be done,
+     *        the swash is stored here now (and av[0] is &PL_sv_undef).
+     *  av[2] stores the inversion list of code points that match only if the
+     *        current locale is UTF-8
+     *  av[3] stores the cp_list inversion list for use in addition or instead
+     *        of av[0]; used only if cp_list exists and av[1] is &PL_sv_undef.
+     *        (Otherwise everything needed is already in av[0] and av[1])
+     *  av[4] is set if any component of the class is from a user-defined
+     *        property; used only if av[3] exists */
+
+    UV n;
+
+    PERL_ARGS_ASSERT_SET_ANYOF_ARG;
+
+    if (! cp_list && ! runtime_defns && ! only_utf8_locale_list) {
+        assert(! (ANYOF_FLAGS(node)
+                    & (ANYOF_UTF8|ANYOF_NONBITMAP_NON_UTF8)));
+       ARG_SET(node, ANYOF_NONBITMAP_EMPTY);
+    }
+    else {
+       AV * const av = newAV();
+       SV *rv;
+
+        assert(ANYOF_FLAGS(node)
+                    & (ANYOF_UTF8|ANYOF_NONBITMAP_NON_UTF8|ANYOF_LOC_FOLD));
+
+       av_store(av, 0, (runtime_defns)
+                       ? SvREFCNT_inc(runtime_defns) : &PL_sv_undef);
+       if (swash) {
+           av_store(av, 1, swash);
+           SvREFCNT_dec_NN(cp_list);
+       }
+       else {
+           av_store(av, 1, &PL_sv_undef);
+           if (cp_list) {
+               av_store(av, 3, cp_list);
+               av_store(av, 4, newSVuv(has_user_defined_property));
+           }
+       }
+
+        if (only_utf8_locale_list) {
+           av_store(av, 2, only_utf8_locale_list);
+        }
+        else {
+           av_store(av, 2, &PL_sv_undef);
+        }
+
+       rv = newRV_noinc(MUTABLE_SV(av));
+       n = add_data(pRExC_state, STR_WITH_LEN("s"));
+       RExC_rxi->data->data[n] = (void*)rv;
+       ARG_SET(node, n);
+    }
+}
+
+
+/* reg_skipcomment()
+
+   Absorbs an /x style # comments from the input stream.
+   Returns true if there is more text remaining in the stream.
+   Will set the REG_RUN_ON_COMMENT_SEEN flag if the comment
+   terminates the pattern without including a newline.
+
+   Note its the callers responsibility to ensure that we are
+   actually in /x mode
+
+*/
+
+STATIC bool
+S_reg_skipcomment(pTHX_ RExC_state_t *pRExC_state)
+{
+    bool ended = 0;
+
+    PERL_ARGS_ASSERT_REG_SKIPCOMMENT;
+
+    while (RExC_parse < RExC_end)
+        if (*RExC_parse++ == '\n') {
+            ended = 1;
+            break;
+        }
+    if (!ended) {
+        /* we ran off the end of the pattern without ending
+           the comment, so we have to add an \n when wrapping */
+        RExC_seen |= REG_RUN_ON_COMMENT_SEEN;
+        return 0;
+    } else
+        return 1;
+}
+
+/* nextchar()
+
+   Advances the parse position, and optionally absorbs
+   "whitespace" from the inputstream.
+
+   Without /x "whitespace" means (?#...) style comments only,
+   with /x this means (?#...) and # comments and whitespace proper.
+
+   Returns the RExC_parse point from BEFORE the scan occurs.
+
+   This is the /x friendly way of saying RExC_parse++.
+*/
+
+STATIC char*
+S_nextchar(pTHX_ RExC_state_t *pRExC_state)
+{
+    char* const retval = RExC_parse++;
+
+    PERL_ARGS_ASSERT_NEXTCHAR;
+
+    for (;;) {
+       if (RExC_end - RExC_parse >= 3
+           && *RExC_parse == '('
+           && RExC_parse[1] == '?'
+           && RExC_parse[2] == '#')
+       {
+           while (*RExC_parse != ')') {
+               if (RExC_parse == RExC_end)
+                   FAIL("Sequence (?#... not terminated");
+               RExC_parse++;
+           }
+           RExC_parse++;
+           continue;
+       }
+       if (RExC_flags & RXf_PMf_EXTENDED) {
+           if (isSPACE(*RExC_parse)) {
+               RExC_parse++;
+               continue;
+           }
+           else if (*RExC_parse == '#') {
+               if ( reg_skipcomment( pRExC_state ) )
+                   continue;
+           }
+       }
+       return retval;
+    }
+}
+
+/*
+- reg_node - emit a node
+*/
+STATIC regnode *                       /* Location. */
+S_reg_node(pTHX_ RExC_state_t *pRExC_state, U8 op)
+{
+    dVAR;
+    regnode *ptr;
+    regnode * const ret = RExC_emit;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REG_NODE;
+
+    if (SIZE_ONLY) {
+       SIZE_ALIGN(RExC_size);
+       RExC_size += 1;
+       return(ret);
+    }
+    if (RExC_emit >= RExC_emit_bound)
+        Perl_croak(aTHX_ "panic: reg_node overrun trying to emit %d, %p>=%p",
+                  op, RExC_emit, RExC_emit_bound);
+
+    NODE_ALIGN_FILL(ret);
+    ptr = ret;
+    FILL_ADVANCE_NODE(ptr, op);
+#ifdef RE_TRACK_PATTERN_OFFSETS
+    if (RExC_offsets) {         /* MJD */
+       MJD_OFFSET_DEBUG(
+              ("%s:%d: (op %s) %s %"UVuf" (len %"UVuf") (max %"UVuf").\n",
+              "reg_node", __LINE__,
+              PL_reg_name[op],
+              (UV)(RExC_emit - RExC_emit_start) > RExC_offsets[0]
+               ? "Overwriting end of array!\n" : "OK",
+              (UV)(RExC_emit - RExC_emit_start),
+              (UV)(RExC_parse - RExC_start),
+              (UV)RExC_offsets[0]));
+       Set_Node_Offset(RExC_emit, RExC_parse + (op == END));
+    }
+#endif
+    RExC_emit = ptr;
+    return(ret);
+}
+
+/*
+- reganode - emit a node with an argument
+*/
+STATIC regnode *                       /* Location. */
+S_reganode(pTHX_ RExC_state_t *pRExC_state, U8 op, U32 arg)
+{
+    dVAR;
+    regnode *ptr;
+    regnode * const ret = RExC_emit;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGANODE;
+
+    if (SIZE_ONLY) {
+       SIZE_ALIGN(RExC_size);
+       RExC_size += 2;
+       /*
+          We can't do this:
+
+          assert(2==regarglen[op]+1);
+
+          Anything larger than this has to allocate the extra amount.
+          If we changed this to be:
+
+          RExC_size += (1 + regarglen[op]);
+
+          then it wouldn't matter. Its not clear what side effect
+          might come from that so its not done so far.
+          -- dmq
+       */
+       return(ret);
+    }
+    if (RExC_emit >= RExC_emit_bound)
+        Perl_croak(aTHX_ "panic: reg_node overrun trying to emit %d, %p>=%p",
+                  op, RExC_emit, RExC_emit_bound);
+
+    NODE_ALIGN_FILL(ret);
+    ptr = ret;
+    FILL_ADVANCE_NODE_ARG(ptr, op, arg);
+#ifdef RE_TRACK_PATTERN_OFFSETS
+    if (RExC_offsets) {         /* MJD */
+       MJD_OFFSET_DEBUG(
+              ("%s(%d): (op %s) %s %"UVuf" <- %"UVuf" (max %"UVuf").\n",
+              "reganode",
+             __LINE__,
+             PL_reg_name[op],
+              (UV)(RExC_emit - RExC_emit_start) > RExC_offsets[0] ?
+              "Overwriting end of array!\n" : "OK",
+              (UV)(RExC_emit - RExC_emit_start),
+              (UV)(RExC_parse - RExC_start),
+              (UV)RExC_offsets[0]));
+       Set_Cur_Node_Offset;
+    }
+#endif
+    RExC_emit = ptr;
+    return(ret);
+}
+
+/*
+- reguni - emit (if appropriate) a Unicode character
+*/
+PERL_STATIC_INLINE STRLEN
+S_reguni(pTHX_ const RExC_state_t *pRExC_state, UV uv, char* s)
+{
+    dVAR;
+
+    PERL_ARGS_ASSERT_REGUNI;
+
+    return SIZE_ONLY ? UNISKIP(uv) : (uvchr_to_utf8((U8*)s, uv) - (U8*)s);
+}
+
+/*
+- reginsert - insert an operator in front of already-emitted operand
+*
+* Means relocating the operand.
+*/
+STATIC void
+S_reginsert(pTHX_ RExC_state_t *pRExC_state, U8 op, regnode *opnd, U32 depth)
+{
+    dVAR;
+    regnode *src;
+    regnode *dst;
+    regnode *place;
+    const int offset = regarglen[(U8)op];
+    const int size = NODE_STEP_REGNODE + offset;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGINSERT;
+    PERL_UNUSED_ARG(depth);
+/* (PL_regkind[(U8)op] == CURLY ? EXTRA_STEP_2ARGS : 0); */
+    DEBUG_PARSE_FMT("inst"," - %s",PL_reg_name[op]);
+    if (SIZE_ONLY) {
+       RExC_size += size;
+       return;
+    }
+
+    src = RExC_emit;
+    RExC_emit += size;
+    dst = RExC_emit;
+    if (RExC_open_parens) {
+        int paren;
+        /*DEBUG_PARSE_FMT("inst"," - %"IVdf, (IV)RExC_npar);*/
+        for ( paren=0 ; paren < RExC_npar ; paren++ ) {
+            if ( RExC_open_parens[paren] >= opnd ) {
+                /*DEBUG_PARSE_FMT("open"," - %d",size);*/
+                RExC_open_parens[paren] += size;
+            } else {
+                /*DEBUG_PARSE_FMT("open"," - %s","ok");*/
+            }
+            if ( RExC_close_parens[paren] >= opnd ) {
+                /*DEBUG_PARSE_FMT("close"," - %d",size);*/
+                RExC_close_parens[paren] += size;
+            } else {
+                /*DEBUG_PARSE_FMT("close"," - %s","ok");*/
+            }
+        }
+    }
+
+    while (src > opnd) {
+       StructCopy(--src, --dst, regnode);
+#ifdef RE_TRACK_PATTERN_OFFSETS
+        if (RExC_offsets) {     /* MJD 20010112 */
+           MJD_OFFSET_DEBUG(
+                 ("%s(%d): (op %s) %s copy %"UVuf" -> %"UVuf" (max %"UVuf").\n",
+                  "reg_insert",
+                 __LINE__,
+                 PL_reg_name[op],
+                  (UV)(dst - RExC_emit_start) > RExC_offsets[0]
+                   ? "Overwriting end of array!\n" : "OK",
+                  (UV)(src - RExC_emit_start),
+                  (UV)(dst - RExC_emit_start),
+                  (UV)RExC_offsets[0]));
+           Set_Node_Offset_To_R(dst-RExC_emit_start, Node_Offset(src));
+           Set_Node_Length_To_R(dst-RExC_emit_start, Node_Length(src));
+        }
+#endif
+    }
+
+
+    place = opnd;              /* Op node, where operand used to be. */
+#ifdef RE_TRACK_PATTERN_OFFSETS
+    if (RExC_offsets) {         /* MJD */
+       MJD_OFFSET_DEBUG(
+              ("%s(%d): (op %s) %s %"UVuf" <- %"UVuf" (max %"UVuf").\n",
+              "reginsert",
+             __LINE__,
+             PL_reg_name[op],
+              (UV)(place - RExC_emit_start) > RExC_offsets[0]
+              ? "Overwriting end of array!\n" : "OK",
+              (UV)(place - RExC_emit_start),
+              (UV)(RExC_parse - RExC_start),
+              (UV)RExC_offsets[0]));
+       Set_Node_Offset(place, RExC_parse);
+       Set_Node_Length(place, 1);
+    }
+#endif
+    src = NEXTOPER(place);
+    FILL_ADVANCE_NODE(place, op);
+    Zero(src, offset, regnode);
+}
+
+/*
+- regtail - set the next-pointer at the end of a node chain of p to val.
+- SEE ALSO: regtail_study
+*/
+/* TODO: All three parms should be const */
+STATIC void
+S_regtail(pTHX_ RExC_state_t *pRExC_state, regnode *p,
+                const regnode *val,U32 depth)
+{
+    dVAR;
+    regnode *scan;
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGTAIL;
+#ifndef DEBUGGING
+    PERL_UNUSED_ARG(depth);
+#endif
+
+    if (SIZE_ONLY)
+       return;
+
+    /* Find last node. */
+    scan = p;
+    for (;;) {
+       regnode * const temp = regnext(scan);
+        DEBUG_PARSE_r({
+            SV * const mysv=sv_newmortal();
+            DEBUG_PARSE_MSG((scan==p ? "tail" : ""));
+            regprop(RExC_rx, mysv, scan, NULL);
+            PerlIO_printf(Perl_debug_log, "~ %s (%d) %s %s\n",
+                SvPV_nolen_const(mysv), REG_NODE_NUM(scan),
+                    (temp == NULL ? "->" : ""),
+                    (temp == NULL ? PL_reg_name[OP(val)] : "")
+            );
+        });
+        if (temp == NULL)
+            break;
+        scan = temp;
+    }
+
+    if (reg_off_by_arg[OP(scan)]) {
+        ARG_SET(scan, val - scan);
+    }
+    else {
+        NEXT_OFF(scan) = val - scan;
+    }
+}
+
+#ifdef DEBUGGING
+/*
+- regtail_study - set the next-pointer at the end of a node chain of p to val.
+- Look for optimizable sequences at the same time.
+- currently only looks for EXACT chains.
+
+This is experimental code. The idea is to use this routine to perform
+in place optimizations on branches and groups as they are constructed,
+with the long term intention of removing optimization from study_chunk so
+that it is purely analytical.
+
+Currently only used when in DEBUG mode. The macro REGTAIL_STUDY() is used
+to control which is which.
+
+*/
+/* TODO: All four parms should be const */
+
+STATIC U8
+S_regtail_study(pTHX_ RExC_state_t *pRExC_state, regnode *p,
+                      const regnode *val,U32 depth)
+{
+    dVAR;
+    regnode *scan;
+    U8 exact = PSEUDO;
+#ifdef EXPERIMENTAL_INPLACESCAN
+    I32 min = 0;
+#endif
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGTAIL_STUDY;
+
+
+    if (SIZE_ONLY)
+        return exact;
+
+    /* Find last node. */
+
+    scan = p;
+    for (;;) {
+        regnode * const temp = regnext(scan);
+#ifdef EXPERIMENTAL_INPLACESCAN
+        if (PL_regkind[OP(scan)] == EXACT) {
+           bool unfolded_multi_char;   /* Unexamined in this routine */
+            if (join_exact(pRExC_state, scan, &min,
+                           &unfolded_multi_char, 1, val, depth+1))
+                return EXACT;
+       }
+#endif
+        if ( exact ) {
+            switch (OP(scan)) {
+                case EXACT:
+                case EXACTF:
+                case EXACTFA_NO_TRIE:
+                case EXACTFA:
+                case EXACTFU:
+                case EXACTFU_SS:
+                case EXACTFL:
+                        if( exact == PSEUDO )
+                            exact= OP(scan);
+                        else if ( exact != OP(scan) )
+                            exact= 0;
+                case NOTHING:
+                    break;
+                default:
+                    exact= 0;
+            }
+        }
+        DEBUG_PARSE_r({
+            SV * const mysv=sv_newmortal();
+            DEBUG_PARSE_MSG((scan==p ? "tsdy" : ""));
+            regprop(RExC_rx, mysv, scan, NULL);
+            PerlIO_printf(Perl_debug_log, "~ %s (%d) -> %s\n",
+                SvPV_nolen_const(mysv),
+                REG_NODE_NUM(scan),
+                PL_reg_name[exact]);
+        });
+       if (temp == NULL)
+           break;
+       scan = temp;
+    }
+    DEBUG_PARSE_r({
+        SV * const mysv_val=sv_newmortal();
+        DEBUG_PARSE_MSG("");
+        regprop(RExC_rx, mysv_val, val, NULL);
+        PerlIO_printf(Perl_debug_log,
+                      "~ attach to %s (%"IVdf") offset to %"IVdf"\n",
+                     SvPV_nolen_const(mysv_val),
+                     (IV)REG_NODE_NUM(val),
+                     (IV)(val - scan)
+        );
+    });
+    if (reg_off_by_arg[OP(scan)]) {
+       ARG_SET(scan, val - scan);
+    }
+    else {
+       NEXT_OFF(scan) = val - scan;
+    }
+
+    return exact;
+}
+#endif
+
+/*
+ - regdump - dump a regexp onto Perl_debug_log in vaguely comprehensible form
+ */
+#ifdef DEBUGGING
+
+static void
+S_regdump_intflags(pTHX_ const char *lead, const U32 flags)
+{
+    int bit;
+    int set=0;
+
+    ASSUME(REG_INTFLAGS_NAME_SIZE <= sizeof(flags)*8);
+
+    for (bit=0; bit<REG_INTFLAGS_NAME_SIZE; bit++) {
+        if (flags & (1<<bit)) {
+            if (!set++ && lead)
+                PerlIO_printf(Perl_debug_log, "%s",lead);
+            PerlIO_printf(Perl_debug_log, "%s ",PL_reg_intflags_name[bit]);
+        }
+    }
+    if (lead)  {
+        if (set)
+            PerlIO_printf(Perl_debug_log, "\n");
+        else
+            PerlIO_printf(Perl_debug_log, "%s[none-set]\n",lead);
+    }
+}
+
+static void
+S_regdump_extflags(pTHX_ const char *lead, const U32 flags)
+{
+    int bit;
+    int set=0;
+    regex_charset cs;
+
+    ASSUME(REG_EXTFLAGS_NAME_SIZE <= sizeof(flags)*8);
+
+    for (bit=0; bit<REG_EXTFLAGS_NAME_SIZE; bit++) {
+        if (flags & (1<<bit)) {
+           if ((1<<bit) & RXf_PMf_CHARSET) {   /* Output separately, below */
+               continue;
+           }
+            if (!set++ && lead)
+                PerlIO_printf(Perl_debug_log, "%s",lead);
+            PerlIO_printf(Perl_debug_log, "%s ",PL_reg_extflags_name[bit]);
+        }
+    }
+    if ((cs = get_regex_charset(flags)) != REGEX_DEPENDS_CHARSET) {
+            if (!set++ && lead) {
+                PerlIO_printf(Perl_debug_log, "%s",lead);
+            }
+            switch (cs) {
+                case REGEX_UNICODE_CHARSET:
+                    PerlIO_printf(Perl_debug_log, "UNICODE");
+                    break;
+                case REGEX_LOCALE_CHARSET:
+                    PerlIO_printf(Perl_debug_log, "LOCALE");
+                    break;
+                case REGEX_ASCII_RESTRICTED_CHARSET:
+                    PerlIO_printf(Perl_debug_log, "ASCII-RESTRICTED");
+                    break;
+                case REGEX_ASCII_MORE_RESTRICTED_CHARSET:
+                    PerlIO_printf(Perl_debug_log, "ASCII-MORE_RESTRICTED");
+                    break;
+                default:
+                    PerlIO_printf(Perl_debug_log, "UNKNOWN CHARACTER SET");
+                    break;
+            }
+    }
+    if (lead)  {
+        if (set)
+            PerlIO_printf(Perl_debug_log, "\n");
+        else
+            PerlIO_printf(Perl_debug_log, "%s[none-set]\n",lead);
+    }
+}
+#endif
+
+void
+Perl_regdump(pTHX_ const regexp *r)
+{
+#ifdef DEBUGGING
+    dVAR;
+    SV * const sv = sv_newmortal();
+    SV *dsv= sv_newmortal();
+    RXi_GET_DECL(r,ri);
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGDUMP;
+
+    (void)dumpuntil(r, ri->program, ri->program + 1, NULL, NULL, sv, 0, 0);
+
+    /* Header fields of interest. */
+    if (r->anchored_substr) {
+       RE_PV_QUOTED_DECL(s, 0, dsv, SvPVX_const(r->anchored_substr),
+           RE_SV_DUMPLEN(r->anchored_substr), 30);
+       PerlIO_printf(Perl_debug_log,
+                     "anchored %s%s at %"IVdf" ",
+                     s, RE_SV_TAIL(r->anchored_substr),
+                     (IV)r->anchored_offset);
+    } else if (r->anchored_utf8) {
+       RE_PV_QUOTED_DECL(s, 1, dsv, SvPVX_const(r->anchored_utf8),
+           RE_SV_DUMPLEN(r->anchored_utf8), 30);
+       PerlIO_printf(Perl_debug_log,
+                     "anchored utf8 %s%s at %"IVdf" ",
+                     s, RE_SV_TAIL(r->anchored_utf8),
+                     (IV)r->anchored_offset);
+    }
+    if (r->float_substr) {
+       RE_PV_QUOTED_DECL(s, 0, dsv, SvPVX_const(r->float_substr),
+           RE_SV_DUMPLEN(r->float_substr), 30);
+       PerlIO_printf(Perl_debug_log,
+                     "floating %s%s at %"IVdf"..%"UVuf" ",
+                     s, RE_SV_TAIL(r->float_substr),
+                     (IV)r->float_min_offset, (UV)r->float_max_offset);
+    } else if (r->float_utf8) {
+       RE_PV_QUOTED_DECL(s, 1, dsv, SvPVX_const(r->float_utf8),
+           RE_SV_DUMPLEN(r->float_utf8), 30);
+       PerlIO_printf(Perl_debug_log,
+                     "floating utf8 %s%s at %"IVdf"..%"UVuf" ",
+                     s, RE_SV_TAIL(r->float_utf8),
+                     (IV)r->float_min_offset, (UV)r->float_max_offset);
+    }
+    if (r->check_substr || r->check_utf8)
+       PerlIO_printf(Perl_debug_log,
+                     (const char *)
+                     (r->check_substr == r->float_substr
+                      && r->check_utf8 == r->float_utf8
+                      ? "(checking floating" : "(checking anchored"));
+    if (r->intflags & PREGf_NOSCAN)
+       PerlIO_printf(Perl_debug_log, " noscan");
+    if (r->extflags & RXf_CHECK_ALL)
+       PerlIO_printf(Perl_debug_log, " isall");
+    if (r->check_substr || r->check_utf8)
+       PerlIO_printf(Perl_debug_log, ") ");
+
+    if (ri->regstclass) {
+       regprop(r, sv, ri->regstclass, NULL);
+       PerlIO_printf(Perl_debug_log, "stclass %s ", SvPVX_const(sv));
+    }
+    if (r->intflags & PREGf_ANCH) {
+       PerlIO_printf(Perl_debug_log, "anchored");
+        if (r->intflags & PREGf_ANCH_BOL)
+           PerlIO_printf(Perl_debug_log, "(BOL)");
+        if (r->intflags & PREGf_ANCH_MBOL)
+           PerlIO_printf(Perl_debug_log, "(MBOL)");
+        if (r->intflags & PREGf_ANCH_SBOL)
+           PerlIO_printf(Perl_debug_log, "(SBOL)");
+        if (r->intflags & PREGf_ANCH_GPOS)
+           PerlIO_printf(Perl_debug_log, "(GPOS)");
+       PerlIO_putc(Perl_debug_log, ' ');
+    }
+    if (r->intflags & PREGf_GPOS_SEEN)
+       PerlIO_printf(Perl_debug_log, "GPOS:%"UVuf" ", (UV)r->gofs);
+    if (r->intflags & PREGf_SKIP)
+       PerlIO_printf(Perl_debug_log, "plus ");
+    if (r->intflags & PREGf_IMPLICIT)
+       PerlIO_printf(Perl_debug_log, "implicit ");
+    PerlIO_printf(Perl_debug_log, "minlen %"IVdf" ", (IV)r->minlen);
+    if (r->extflags & RXf_EVAL_SEEN)
+       PerlIO_printf(Perl_debug_log, "with eval ");
+    PerlIO_printf(Perl_debug_log, "\n");
+    DEBUG_FLAGS_r({
+        regdump_extflags("r->extflags: ",r->extflags);
+        regdump_intflags("r->intflags: ",r->intflags);
+    });
+#else
+    PERL_ARGS_ASSERT_REGDUMP;
+    PERL_UNUSED_CONTEXT;
+    PERL_UNUSED_ARG(r);
+#endif /* DEBUGGING */
+}
+
+/*
+- regprop - printable representation of opcode, with run time support
+*/
+
+void
+Perl_regprop(pTHX_ const regexp *prog, SV *sv, const regnode *o, const regmatch_info *reginfo)
+{
+#ifdef DEBUGGING
+    dVAR;
+    int k;
+
+    /* Should be synchronized with * ANYOF_ #xdefines in regcomp.h */
+    static const char * const anyofs[] = {
+#if _CC_WORDCHAR != 0 || _CC_DIGIT != 1 || _CC_ALPHA != 2 || _CC_LOWER != 3 \
+    || _CC_UPPER != 4 || _CC_PUNCT != 5 || _CC_PRINT != 6                   \
+    || _CC_ALPHANUMERIC != 7 || _CC_GRAPH != 8 || _CC_CASED != 9            \
+    || _CC_SPACE != 10 || _CC_BLANK != 11 || _CC_XDIGIT != 12               \
+    || _CC_PSXSPC != 13 || _CC_CNTRL != 14 || _CC_ASCII != 15               \
+    || _CC_VERTSPACE != 16
+  #error Need to adjust order of anyofs[]
+#endif
+        "\\w",
+        "\\W",
+        "\\d",
+        "\\D",
+        "[:alpha:]",
+        "[:^alpha:]",
+        "[:lower:]",
+        "[:^lower:]",
+        "[:upper:]",
+        "[:^upper:]",
+        "[:punct:]",
+        "[:^punct:]",
+        "[:print:]",
+        "[:^print:]",
+        "[:alnum:]",
+        "[:^alnum:]",
+        "[:graph:]",
+        "[:^graph:]",
+        "[:cased:]",
+        "[:^cased:]",
+        "\\s",
+        "\\S",
+        "[:blank:]",
+        "[:^blank:]",
+        "[:xdigit:]",
+        "[:^xdigit:]",
+        "[:space:]",
+        "[:^space:]",
+        "[:cntrl:]",
+        "[:^cntrl:]",
+        "[:ascii:]",
+        "[:^ascii:]",
+        "\\v",
+        "\\V"
+    };
+    RXi_GET_DECL(prog,progi);
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGPROP;
+
+    sv_setpvs(sv, "");
+
+    if (OP(o) > REGNODE_MAX)           /* regnode.type is unsigned */
+       /* It would be nice to FAIL() here, but this may be called from
+          regexec.c, and it would be hard to supply pRExC_state. */
+       Perl_croak(aTHX_ "Corrupted regexp opcode %d > %d",
+                                              (int)OP(o), (int)REGNODE_MAX);
+    sv_catpv(sv, PL_reg_name[OP(o)]); /* Take off const! */
+
+    k = PL_regkind[OP(o)];
+
+    if (k == EXACT) {
+       sv_catpvs(sv, " ");
+       /* Using is_utf8_string() (via PERL_PV_UNI_DETECT)
+        * is a crude hack but it may be the best for now since
+        * we have no flag "this EXACTish node was UTF-8"
+        * --jhi */
+       pv_pretty(sv, STRING(o), STR_LEN(o), 60, PL_colors[0], PL_colors[1],
+                 PERL_PV_ESCAPE_UNI_DETECT |
+                 PERL_PV_ESCAPE_NONASCII   |
+                 PERL_PV_PRETTY_ELLIPSES   |
+                 PERL_PV_PRETTY_LTGT       |
+                 PERL_PV_PRETTY_NOCLEAR
+                 );
+    } else if (k == TRIE) {
+       /* print the details of the trie in dumpuntil instead, as
+        * progi->data isn't available here */
+        const char op = OP(o);
+        const U32 n = ARG(o);
+        const reg_ac_data * const ac = IS_TRIE_AC(op) ?
+               (reg_ac_data *)progi->data->data[n] :
+               NULL;
+        const reg_trie_data * const trie
+           = (reg_trie_data*)progi->data->data[!IS_TRIE_AC(op) ? n : ac->trie];
+
+        Perl_sv_catpvf(aTHX_ sv, "-%s",PL_reg_name[o->flags]);
+        DEBUG_TRIE_COMPILE_r(
+          Perl_sv_catpvf(aTHX_ sv,
+            "<S:%"UVuf"/%"IVdf" W:%"UVuf" L:%"UVuf"/%"UVuf" C:%"UVuf"/%"UVuf">",
+            (UV)trie->startstate,
+            (IV)trie->statecount-1, /* -1 because of the unused 0 element */
+            (UV)trie->wordcount,
+            (UV)trie->minlen,
+            (UV)trie->maxlen,
+            (UV)TRIE_CHARCOUNT(trie),
+            (UV)trie->uniquecharcount
+          );
+        );
+        if ( IS_ANYOF_TRIE(op) || trie->bitmap ) {
+            sv_catpvs(sv, "[");
+            (void) put_latin1_charclass_innards(sv, IS_ANYOF_TRIE(op)
+                                                   ? ANYOF_BITMAP(o)
+                                                   : TRIE_BITMAP(trie));
+            sv_catpvs(sv, "]");
+        }
+
+    } else if (k == CURLY) {
+       if (OP(o) == CURLYM || OP(o) == CURLYN || OP(o) == CURLYX)
+           Perl_sv_catpvf(aTHX_ sv, "[%d]", o->flags); /* Parenth number */
+       Perl_sv_catpvf(aTHX_ sv, " {%d,%d}", ARG1(o), ARG2(o));
+    }
+    else if (k == WHILEM && o->flags)                  /* Ordinal/of */
+       Perl_sv_catpvf(aTHX_ sv, "[%d/%d]", o->flags & 0xf, o->flags>>4);
+    else if (k == REF || k == OPEN || k == CLOSE
+             || k == GROUPP || OP(o)==ACCEPT)
+    {
+       Perl_sv_catpvf(aTHX_ sv, "%d", (int)ARG(o));    /* Parenth number */
+       if ( RXp_PAREN_NAMES(prog) ) {
+            if ( k != REF || (OP(o) < NREF)) {
+               AV *list= MUTABLE_AV(progi->data->data[progi->name_list_idx]);
+               SV **name= av_fetch(list, ARG(o), 0 );
+               if (name)
+                   Perl_sv_catpvf(aTHX_ sv, " '%"SVf"'", SVfARG(*name));
+            }
+            else {
+                AV *list= MUTABLE_AV(progi->data->data[ progi->name_list_idx ]);
+                SV *sv_dat= MUTABLE_SV(progi->data->data[ ARG( o ) ]);
+                I32 *nums=(I32*)SvPVX(sv_dat);
+                SV **name= av_fetch(list, nums[0], 0 );
+                I32 n;
+                if (name) {
+                    for ( n=0; n<SvIVX(sv_dat); n++ ) {
+                        Perl_sv_catpvf(aTHX_ sv, "%s%"IVdf,
+                                   (n ? "," : ""), (IV)nums[n]);
+                    }
+                    Perl_sv_catpvf(aTHX_ sv, " '%"SVf"'", SVfARG(*name));
+                }
+            }
+        }
+        if ( k == REF && reginfo) {
+            U32 n = ARG(o);  /* which paren pair */
+            I32 ln = prog->offs[n].start;
+            if (prog->lastparen < n || ln == -1)
+                Perl_sv_catpvf(aTHX_ sv, ": FAIL");
+            else if (ln == prog->offs[n].end)
+                Perl_sv_catpvf(aTHX_ sv, ": ACCEPT - EMPTY STRING");
+            else {
+                const char *s = reginfo->strbeg + ln;
+                Perl_sv_catpvf(aTHX_ sv, ": ");
+                Perl_pv_pretty( aTHX_ sv, s, prog->offs[n].end - prog->offs[n].start, 32, 0, 0,
+                    PERL_PV_ESCAPE_UNI_DETECT|PERL_PV_PRETTY_NOCLEAR|PERL_PV_PRETTY_ELLIPSES|PERL_PV_PRETTY_QUOTE );
+            }
+        }
+    } else if (k == GOSUB)
+        /* Paren and offset */
+       Perl_sv_catpvf(aTHX_ sv, "%d[%+d]", (int)ARG(o),(int)ARG2L(o));
+    else if (k == VERB) {
+        if (!o->flags)
+            Perl_sv_catpvf(aTHX_ sv, ":%"SVf,
+                          SVfARG((MUTABLE_SV(progi->data->data[ ARG( o ) ]))));
+    } else if (k == LOGICAL)
+        /* 2: embedded, otherwise 1 */
+       Perl_sv_catpvf(aTHX_ sv, "[%d]", o->flags);
+    else if (k == ANYOF) {
+       const U8 flags = ANYOF_FLAGS(o);
+       int do_sep = 0;
+
+
+       if (flags & ANYOF_LOCALE_FLAGS)
+           sv_catpvs(sv, "{loc}");
+       if (flags & ANYOF_LOC_FOLD)
+           sv_catpvs(sv, "{i}");
+       Perl_sv_catpvf(aTHX_ sv, "[%s", PL_colors[0]);
+       if (flags & ANYOF_INVERT)
+           sv_catpvs(sv, "^");
+
+       /* output what the standard cp 0-255 bitmap matches */
+        do_sep = put_latin1_charclass_innards(sv, ANYOF_BITMAP(o));
+
+        /* output any special charclass tests (used entirely under use
+         * locale) * */
+       if (ANYOF_POSIXL_TEST_ANY_SET(o)) {
+            int i;
+           for (i = 0; i < ANYOF_POSIXL_MAX; i++) {
+               if (ANYOF_POSIXL_TEST(o,i)) {
+                   sv_catpv(sv, anyofs[i]);
+                   do_sep = 1;
+               }
+            }
+        }
+
+       if ((flags & (ANYOF_ABOVE_LATIN1_ALL
+                      |ANYOF_UTF8
+                      |ANYOF_NONBITMAP_NON_UTF8
+                      |ANYOF_LOC_FOLD)))
+        {
+            if (do_sep) {
+                Perl_sv_catpvf(aTHX_ sv,"%s][%s",PL_colors[1],PL_colors[0]);
+                if (flags & ANYOF_INVERT)
+                    /*make sure the invert info is in each */
+                    sv_catpvs(sv, "^");
+            }
+
+            if (flags & ANYOF_NON_UTF8_NON_ASCII_ALL) {
+                sv_catpvs(sv, "{non-utf8-latin1-all}");
+            }
+
+            /* output information about the unicode matching */
+            if (flags & ANYOF_ABOVE_LATIN1_ALL)
+                sv_catpvs(sv, "{unicode_all}");
+            else if (ARG(o) != ANYOF_NONBITMAP_EMPTY) {
+                SV *lv; /* Set if there is something outside the bit map. */
+                bool byte_output = FALSE;   /* If something in the bitmap has
+                                               been output */
+                SV *only_utf8_locale;
+
+                /* Get the stuff that wasn't in the bitmap */
+                (void) _get_regclass_nonbitmap_data(prog, o, FALSE,
+                                                    &lv, &only_utf8_locale);
+                if (lv && lv != &PL_sv_undef) {
+                    char *s = savesvpv(lv);
+                    char * const origs = s;
+
+                    while (*s && *s != '\n')
+                        s++;
+
+                    if (*s == '\n') {
+                        const char * const t = ++s;
+
+                        if (flags & ANYOF_NONBITMAP_NON_UTF8) {
+                            sv_catpvs(sv, "{outside bitmap}");
+                        }
+                        else {
+                            sv_catpvs(sv, "{utf8}");
+                        }
+
+                        if (byte_output) {
+                            sv_catpvs(sv, " ");
+                        }
+
+                        while (*s) {
+                            if (*s == '\n') {
+
+                                /* Truncate very long output */
+                                if (s - origs > 256) {
+                                    Perl_sv_catpvf(aTHX_ sv,
+                                                "%.*s...",
+                                                (int) (s - origs - 1),
+                                                t);
+                                    goto out_dump;
+                                }
+                                *s = ' ';
+                            }
+                            else if (*s == '\t') {
+                                *s = '-';
+                            }
+                            s++;
+                        }
+                        if (s[-1] == ' ')
+                            s[-1] = 0;
+
+                        sv_catpv(sv, t);
+                    }
+
+                out_dump:
+
+                    Safefree(origs);
+                    SvREFCNT_dec_NN(lv);
+                }
+
+                if ((flags & ANYOF_LOC_FOLD)
+                     && only_utf8_locale
+                     && only_utf8_locale != &PL_sv_undef)
+                {
+                    UV start, end;
+                    int max_entries = 256;
+
+                    sv_catpvs(sv, "{utf8 locale}");
+                    invlist_iterinit(only_utf8_locale);
+                    while (invlist_iternext(only_utf8_locale,
+                                            &start, &end)) {
+                        put_range(sv, start, end);
+                        max_entries --;
+                        if (max_entries < 0) {
+                            sv_catpvs(sv, "...");
+                            break;
+                        }
+                    }
+                    invlist_iterfinish(only_utf8_locale);
+                }
+            }
+       }
+
+       Perl_sv_catpvf(aTHX_ sv, "%s]", PL_colors[1]);
+    }
+    else if (k == POSIXD || k == NPOSIXD) {
+        U8 index = FLAGS(o) * 2;
+        if (index < C_ARRAY_LENGTH(anyofs)) {
+            if (*anyofs[index] != '[')  {
+                sv_catpv(sv, "[");
+            }
+            sv_catpv(sv, anyofs[index]);
+            if (*anyofs[index] != '[')  {
+                sv_catpv(sv, "]");
+            }
+        }
+        else {
+            Perl_sv_catpvf(aTHX_ sv, "[illegal type=%d])", index);
+        }
+    }
+    else if (k == BRANCHJ && (OP(o) == UNLESSM || OP(o) == IFMATCH))
+       Perl_sv_catpvf(aTHX_ sv, "[%d]", -(o->flags));
+#else
+    PERL_UNUSED_CONTEXT;
+    PERL_UNUSED_ARG(sv);
+    PERL_UNUSED_ARG(o);
+    PERL_UNUSED_ARG(prog);
+    PERL_UNUSED_ARG(reginfo);
+#endif /* DEBUGGING */
+}
+
+
+
+SV *
+Perl_re_intuit_string(pTHX_ REGEXP * const r)
+{                              /* Assume that RE_INTUIT is set */
+    dVAR;
+    struct regexp *const prog = ReANY(r);
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_RE_INTUIT_STRING;
+    PERL_UNUSED_CONTEXT;
+
+    DEBUG_COMPILE_r(
+       {
+           const char * const s = SvPV_nolen_const(prog->check_substr
+                     ? prog->check_substr : prog->check_utf8);
+
+           if (!PL_colorset) reginitcolors();
+           PerlIO_printf(Perl_debug_log,
+                     "%sUsing REx %ssubstr:%s \"%s%.60s%s%s\"\n",
+                     PL_colors[4],
+                     prog->check_substr ? "" : "utf8 ",
+                     PL_colors[5],PL_colors[0],
+                     s,
+                     PL_colors[1],
+                     (strlen(s) > 60 ? "..." : ""));
+       } );
+
+    return prog->check_substr ? prog->check_substr : prog->check_utf8;
+}
+
+/*
+   pregfree()
+
+   handles refcounting and freeing the perl core regexp structure. When
+   it is necessary to actually free the structure the first thing it
+   does is call the 'free' method of the regexp_engine associated to
+   the regexp, allowing the handling of the void *pprivate; member
+   first. (This routine is not overridable by extensions, which is why
+   the extensions free is called first.)
+
+   See regdupe and regdupe_internal if you change anything here.
+*/
+#ifndef PERL_IN_XSUB_RE
+void
+Perl_pregfree(pTHX_ REGEXP *r)
+{
+    SvREFCNT_dec(r);
+}
+
+void
+Perl_pregfree2(pTHX_ REGEXP *rx)
+{
+    dVAR;
+    struct regexp *const r = ReANY(rx);
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_PREGFREE2;
+
+    if (r->mother_re) {
+        ReREFCNT_dec(r->mother_re);
+    } else {
+        CALLREGFREE_PVT(rx); /* free the private data */
+        SvREFCNT_dec(RXp_PAREN_NAMES(r));
+       Safefree(r->xpv_len_u.xpvlenu_pv);
+    }
+    if (r->substrs) {
+        SvREFCNT_dec(r->anchored_substr);
+        SvREFCNT_dec(r->anchored_utf8);
+        SvREFCNT_dec(r->float_substr);
+        SvREFCNT_dec(r->float_utf8);
+       Safefree(r->substrs);
+    }
+    RX_MATCH_COPY_FREE(rx);
+#ifdef PERL_ANY_COW
+    SvREFCNT_dec(r->saved_copy);
+#endif
+    Safefree(r->offs);
+    SvREFCNT_dec(r->qr_anoncv);
+    rx->sv_u.svu_rx = 0;
+}
+
+/*  reg_temp_copy()
+
+    This is a hacky workaround to the structural issue of match results
+    being stored in the regexp structure which is in turn stored in
+    PL_curpm/PL_reg_curpm. The problem is that due to qr// the pattern
+    could be PL_curpm in multiple contexts, and could require multiple
+    result sets being associated with the pattern simultaneously, such
+    as when doing a recursive match with (??{$qr})
+
+    The solution is to make a lightweight copy of the regexp structure
+    when a qr// is returned from the code executed by (??{$qr}) this
+    lightweight copy doesn't actually own any of its data except for
+    the starp/end and the actual regexp structure itself.
+
+*/
+
+
+REGEXP *
+Perl_reg_temp_copy (pTHX_ REGEXP *ret_x, REGEXP *rx)
+{
+    struct regexp *ret;
+    struct regexp *const r = ReANY(rx);
+    const bool islv = ret_x && SvTYPE(ret_x) == SVt_PVLV;
+
+    PERL_ARGS_ASSERT_REG_TEMP_COPY;
+
+    if (!ret_x)
+       ret_x = (REGEXP*) newSV_type(SVt_REGEXP);
+    else {
+       SvOK_off((SV *)ret_x);
+       if (islv) {
+           /* For PVLVs, SvANY points to the xpvlv body while sv_u points
+              to the regexp.  (For SVt_REGEXPs, sv_upgrade has already
+              made both spots point to the same regexp body.) */
+           REGEXP *temp = (REGEXP *)newSV_type(SVt_REGEXP);
+           assert(!SvPVX(ret_x));
+           ret_x->sv_u.svu_rx = temp->sv_any;
+           temp->sv_any = NULL;
+           SvFLAGS(temp) = (SvFLAGS(temp) & ~SVTYPEMASK) | SVt_NULL;
+           SvREFCNT_dec_NN(temp);
+           /* SvCUR still resides in the xpvlv struct, so the regexp copy-
+              ing below will not set it. */
+           SvCUR_set(ret_x, SvCUR(rx));
+       }
+    }
+    /* This ensures that SvTHINKFIRST(sv) is true, and hence that
+       sv_force_normal(sv) is called.  */
+    SvFAKE_on(ret_x);
+    ret = ReANY(ret_x);
+
+    SvFLAGS(ret_x) |= SvUTF8(rx);
+    /* We share the same string buffer as the original regexp, on which we
+       hold a reference count, incremented when mother_re is set below.
+       The string pointer is copied here, being part of the regexp struct.
+     */
+    memcpy(&(ret->xpv_cur), &(r->xpv_cur),
+          sizeof(regexp) - STRUCT_OFFSET(regexp, xpv_cur));
+    if (r->offs) {
+        const I32 npar = r->nparens+1;
+        Newx(ret->offs, npar, regexp_paren_pair);
+        Copy(r->offs, ret->offs, npar, regexp_paren_pair);
+    }
+    if (r->substrs) {
+        Newx(ret->substrs, 1, struct reg_substr_data);
+       StructCopy(r->substrs, ret->substrs, struct reg_substr_data);
+
+       SvREFCNT_inc_void(ret->anchored_substr);
+       SvREFCNT_inc_void(ret->anchored_utf8);
+       SvREFCNT_inc_void(ret->float_substr);
+       SvREFCNT_inc_void(ret->float_utf8);
+
+       /* check_substr and check_utf8, if non-NULL, point to either their
+          anchored or float namesakes, and don't hold a second reference.  */
+    }
+    RX_MATCH_COPIED_off(ret_x);
+#ifdef PERL_ANY_COW
+    ret->saved_copy = NULL;
+#endif
+    ret->mother_re = ReREFCNT_inc(r->mother_re ? r->mother_re : rx);
+    SvREFCNT_inc_void(ret->qr_anoncv);
+
+    return ret_x;
+}
+#endif
+
+/* regfree_internal()
+
+   Free the private data in a regexp. This is overloadable by
+   extensions. Perl takes care of the regexp structure in pregfree(),
+   this covers the *pprivate pointer which technically perl doesn't
+   know about, however of course we have to handle the
+   regexp_internal structure when no extension is in use.
+
+   Note this is called before freeing anything in the regexp
+   structure.
+ */
+
+void
+Perl_regfree_internal(pTHX_ REGEXP * const rx)
+{
+    dVAR;
+    struct regexp *const r = ReANY(rx);
+    RXi_GET_DECL(r,ri);
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_REGFREE_INTERNAL;
+
+    DEBUG_COMPILE_r({
+       if (!PL_colorset)
+           reginitcolors();
+       {
+           SV *dsv= sv_newmortal();
+            RE_PV_QUOTED_DECL(s, RX_UTF8(rx),
+                dsv, RX_PRECOMP(rx), RX_PRELEN(rx), 60);
+            PerlIO_printf(Perl_debug_log,"%sFreeing REx:%s %s\n",
+                PL_colors[4],PL_colors[5],s);
+        }
+    });
+#ifdef RE_TRACK_PATTERN_OFFSETS
+    if (ri->u.offsets)
+        Safefree(ri->u.offsets);             /* 20010421 MJD */
+#endif
+    if (ri->code_blocks) {
+       int n;
+       for (n = 0; n < ri->num_code_blocks; n++)
+           SvREFCNT_dec(ri->code_blocks[n].src_regex);
+       Safefree(ri->code_blocks);
+    }
+
+    if (ri->data) {
+       int n = ri->data->count;
+
+       while (--n >= 0) {
+          /* If you add a ->what type here, update the comment in regcomp.h */
+           switch (ri->data->what[n]) {
+           case 'a':
+           case 'r':
+           case 's':
+           case 'S':
+           case 'u':
+               SvREFCNT_dec(MUTABLE_SV(ri->data->data[n]));
+               break;
+           case 'f':
+               Safefree(ri->data->data[n]);
+               break;
+           case 'l':
+           case 'L':
+               break;
+            case 'T':
+                { /* Aho Corasick add-on structure for a trie node.
+                     Used in stclass optimization only */
+                    U32 refcount;
+                    reg_ac_data *aho=(reg_ac_data*)ri->data->data[n];
+                    OP_REFCNT_LOCK;
+                    refcount = --aho->refcount;
+                    OP_REFCNT_UNLOCK;
+                    if ( !refcount ) {
+                        PerlMemShared_free(aho->states);
+                        PerlMemShared_free(aho->fail);
+                        /* do this last!!!! */
+                        PerlMemShared_free(ri->data->data[n]);
+                        PerlMemShared_free(ri->regstclass);
+                    }
+                }
+                break;
+           case 't':
+               {
+                   /* trie structure. */
+                   U32 refcount;
+                   reg_trie_data *trie=(reg_trie_data*)ri->data->data[n];
+                    OP_REFCNT_LOCK;
+                    refcount = --trie->refcount;
+                    OP_REFCNT_UNLOCK;
+                    if ( !refcount ) {
+                        PerlMemShared_free(trie->charmap);
+                        PerlMemShared_free(trie->states);
+                        PerlMemShared_free(trie->trans);
+                        if (trie->bitmap)
+                            PerlMemShared_free(trie->bitmap);
+                        if (trie->jump)
+                            PerlMemShared_free(trie->jump);
+                       PerlMemShared_free(trie->wordinfo);
+                        /* do this last!!!! */
+                        PerlMemShared_free(ri->data->data[n]);
+                   }
+               }
+               break;
+           default:
+               Perl_croak(aTHX_ "panic: regfree data code '%c'",
+                                                    ri->data->what[n]);
+           }
+       }
+       Safefree(ri->data->what);
+       Safefree(ri->data);
+    }
+
+    Safefree(ri);
+}
+
+#define av_dup_inc(s,t)        MUTABLE_AV(sv_dup_inc((const SV *)s,t))
+#define hv_dup_inc(s,t)        MUTABLE_HV(sv_dup_inc((const SV *)s,t))
+#define SAVEPVN(p,n)   ((p) ? savepvn(p,n) : NULL)
+
+/*
+   re_dup - duplicate a regexp.
+
+   This routine is expected to clone a given regexp structure. It is only
+   compiled under USE_ITHREADS.
+
+   After all of the core data stored in struct regexp is duplicated
+   the regexp_engine.dupe method is used to copy any private data
+   stored in the *pprivate pointer. This allows extensions to handle
+   any duplication it needs to do.
+
+   See pregfree() and regfree_internal() if you change anything here.
+*/
+#if defined(USE_ITHREADS)
+#ifndef PERL_IN_XSUB_RE
+void
+Perl_re_dup_guts(pTHX_ const REGEXP *sstr, REGEXP *dstr, CLONE_PARAMS *param)
+{
+    dVAR;
+    I32 npar;
+    const struct regexp *r = ReANY(sstr);
+    struct regexp *ret = ReANY(dstr);
+
+    PERL_ARGS_ASSERT_RE_DUP_GUTS;
+
+    npar = r->nparens+1;
+    Newx(ret->offs, npar, regexp_paren_pair);
+    Copy(r->offs, ret->offs, npar, regexp_paren_pair);
+
+    if (ret->substrs) {
+       /* Do it this way to avoid reading from *r after the StructCopy().
+          That way, if any of the sv_dup_inc()s dislodge *r from the L1
+          cache, it doesn't matter.  */
+       const bool anchored = r->check_substr
+           ? r->check_substr == r->anchored_substr
+           : r->check_utf8 == r->anchored_utf8;
+        Newx(ret->substrs, 1, struct reg_substr_data);
+       StructCopy(r->substrs, ret->substrs, struct reg_substr_data);
+
+       ret->anchored_substr = sv_dup_inc(ret->anchored_substr, param);
+       ret->anchored_utf8 = sv_dup_inc(ret->anchored_utf8, param);
+       ret->float_substr = sv_dup_inc(ret->float_substr, param);
+       ret->float_utf8 = sv_dup_inc(ret->float_utf8, param);
+
+       /* check_substr and check_utf8, if non-NULL, point to either their
+          anchored or float namesakes, and don't hold a second reference.  */
+
+       if (ret->check_substr) {
+           if (anchored) {
+               assert(r->check_utf8 == r->anchored_utf8);
+               ret->check_substr = ret->anchored_substr;
+               ret->check_utf8 = ret->anchored_utf8;
+           } else {
+               assert(r->check_substr == r->float_substr);
+               assert(r->check_utf8 == r->float_utf8);
+               ret->check_substr = ret->float_substr;
+               ret->check_utf8 = ret->float_utf8;
+           }
+       } else if (ret->check_utf8) {
+           if (anchored) {
+               ret->check_utf8 = ret->anchored_utf8;
+           } else {
+               ret->check_utf8 = ret->float_utf8;
+           }
+       }
+    }
+
+    RXp_PAREN_NAMES(ret) = hv_dup_inc(RXp_PAREN_NAMES(ret), param);
+    ret->qr_anoncv = MUTABLE_CV(sv_dup_inc((const SV *)ret->qr_anoncv, param));
+
+    if (ret->pprivate)
+       RXi_SET(ret,CALLREGDUPE_PVT(dstr,param));
+
+    if (RX_MATCH_COPIED(dstr))
+       ret->subbeg  = SAVEPVN(ret->subbeg, ret->sublen);
+    else
+       ret->subbeg = NULL;
+#ifdef PERL_ANY_COW
+    ret->saved_copy = NULL;
+#endif
+
+    /* Whether mother_re be set or no, we need to copy the string.  We
+       cannot refrain from copying it when the storage points directly to
+       our mother regexp, because that's
+              1: a buffer in a different thread
+              2: something we no longer hold a reference on
+              so we need to copy it locally.  */
+    RX_WRAPPED(dstr) = SAVEPVN(RX_WRAPPED(sstr), SvCUR(sstr)+1);
+    ret->mother_re   = NULL;
+}
+#endif /* PERL_IN_XSUB_RE */
+
+/*
+   regdupe_internal()
+
+   This is the internal complement to regdupe() which is used to copy
+   the structure pointed to by the *pprivate pointer in the regexp.
+   This is the core version of the extension overridable cloning hook.
+   The regexp structure being duplicated will be copied by perl prior
+   to this and will be provided as the regexp *r argument, however
+   with the /old/ structures pprivate pointer value. Thus this routine
+   may override any copying normally done by perl.
+
+   It returns a pointer to the new regexp_internal structure.
+*/
+
+void *
+Perl_regdupe_internal(pTHX_ REGEXP * const rx, CLONE_PARAMS *param)
+{
+    dVAR;
+    struct regexp *const r = ReANY(rx);
+    regexp_internal *reti;
+    int len;
+    RXi_GET_DECL(r,ri);
+
+    PERL_ARGS_ASSERT_REGDUPE_INTERNAL;
+
+    len = ProgLen(ri);
+
+    Newxc(reti, sizeof(regexp_internal) + len*sizeof(regnode),
+          char, regexp_internal);
+    Copy(ri->program, reti->program, len+1, regnode);
+
+    reti->num_code_blocks = ri->num_code_blocks;
+    if (ri->code_blocks) {
+       int n;
+       Newxc(reti->code_blocks, ri->num_code_blocks, struct reg_code_block,
+               struct reg_code_block);
+       Copy(ri->code_blocks, reti->code_blocks, ri->num_code_blocks,
+               struct reg_code_block);
+       for (n = 0; n < ri->num_code_blocks; n++)
+            reti->code_blocks[n].src_regex = (REGEXP*)
+                   sv_dup_inc((SV*)(ri->code_blocks[n].src_regex), param);
+    }
+    else
+       reti->code_blocks = NULL;
+
+    reti->regstclass = NULL;
+
+    if (ri->data) {
+       struct reg_data *d;
+        const int count = ri->data->count;
+       int i;
+
+       Newxc(d, sizeof(struct reg_data) + count*sizeof(void *),
+               char, struct reg_data);
+       Newx(d->what, count, U8);
+
+       d->count = count;
+       for (i = 0; i < count; i++) {
+           d->what[i] = ri->data->what[i];
+           switch (d->what[i]) {
+               /* see also regcomp.h and regfree_internal() */
+           case 'a': /* actually an AV, but the dup function is identical.  */
+           case 'r':
+           case 's':
+           case 'S':
+           case 'u': /* actually an HV, but the dup function is identical.  */
+               d->data[i] = sv_dup_inc((const SV *)ri->data->data[i], param);
+               break;
+           case 'f':
+               /* This is cheating. */
+               Newx(d->data[i], 1, regnode_ssc);
+               StructCopy(ri->data->data[i], d->data[i], regnode_ssc);
+               reti->regstclass = (regnode*)d->data[i];
+               break;
+           case 'T':
+               /* Trie stclasses are readonly and can thus be shared
+                * without duplication. We free the stclass in pregfree
+                * when the corresponding reg_ac_data struct is freed.
+                */
+               reti->regstclass= ri->regstclass;
+               /* Fall through */
+           case 't':
+               OP_REFCNT_LOCK;
+               ((reg_trie_data*)ri->data->data[i])->refcount++;
+               OP_REFCNT_UNLOCK;
+               /* Fall through */
+           case 'l':
+           case 'L':
+               d->data[i] = ri->data->data[i];
+               break;
+            default:
+               Perl_croak(aTHX_ "panic: re_dup unknown data code '%c'",
+                                                           ri->data->what[i]);
+           }
+       }
+
+       reti->data = d;
+    }
+    else
+       reti->data = NULL;
+
+    reti->name_list_idx = ri->name_list_idx;
+
+#ifdef RE_TRACK_PATTERN_OFFSETS
+    if (ri->u.offsets) {
+        Newx(reti->u.offsets, 2*len+1, U32);
+        Copy(ri->u.offsets, reti->u.offsets, 2*len+1, U32);
+    }
+#else
+    SetProgLen(reti,len);
+#endif
+
+    return (void*)reti;
+}
+
+#endif    /* USE_ITHREADS */
+
+#ifndef PERL_IN_XSUB_RE
+
+/*
+ - regnext - dig the "next" pointer out of a node
+ */
+regnode *
+Perl_regnext(pTHX_ regnode *p)
+{
+    dVAR;
+    I32 offset;
+
+    if (!p)
+       return(NULL);
+
+    if (OP(p) > REGNODE_MAX) {         /* regnode.type is unsigned */
+       Perl_croak(aTHX_ "Corrupted regexp opcode %d > %d",
+                                                (int)OP(p), (int)REGNODE_MAX);
+    }
+
+    offset = (reg_off_by_arg[OP(p)] ? ARG(p) : NEXT_OFF(p));
+    if (offset == 0)
+       return(NULL);
+
+    return(p+offset);
+}
+#endif
+
+STATIC void
+S_re_croak2(pTHX_ bool utf8, const char* pat1,const char* pat2,...)
+{
+    va_list args;
+    STRLEN l1 = strlen(pat1);
+    STRLEN l2 = strlen(pat2);
+    char buf[512];
+    SV *msv;
+    const char *message;
+
+    PERL_ARGS_ASSERT_RE_CROAK2;
+
+    if (l1 > 510)
+       l1 = 510;
+    if (l1 + l2 > 510)
+       l2 = 510 - l1;
+    Copy(pat1, buf, l1 , char);
+    Copy(pat2, buf + l1, l2 , char);
+    buf[l1 + l2] = '\n';
+    buf[l1 + l2 + 1] = '\0';
+    va_start(args, pat2);
+    msv = vmess(buf, &args);
+    va_end(args);
+    message = SvPV_const(msv,l1);
+    if (l1 > 512)
+       l1 = 512;
+    Copy(message, buf, l1 , char);
+    /* l1-1 to avoid \n */
+    Perl_croak(aTHX_ "%"UTF8f, UTF8fARG(utf8, l1-1, buf));
+}
+
+/* XXX Here's a total kludge.  But we need to re-enter for swash routines. */
+
+#ifndef PERL_IN_XSUB_RE
+void
+Perl_save_re_context(pTHX)
+{
+    dVAR;
+
+    /* Save $1..$n (#18107: UTF-8 s/(\w+)/uc($1)/e); AMS 20021106. */
+    if (PL_curpm) {
+       const REGEXP * const rx = PM_GETRE(PL_curpm);
+       if (rx) {
+           U32 i;
+           for (i = 1; i <= RX_NPARENS(rx); i++) {
+               char digits[TYPE_CHARS(long)];
+               const STRLEN len = my_snprintf(digits, sizeof(digits),
+                                               "%lu", (long)i);
+               GV *const *const gvp
+                   = (GV**)hv_fetch(PL_defstash, digits, len, 0);
+
+               if (gvp) {
+                   GV * const gv = *gvp;
+                   if (SvTYPE(gv) == SVt_PVGV && GvSV(gv))
+                       save_scalar(gv);
+               }
+           }
+       }
+    }
+}
+#endif
+
+#ifdef DEBUGGING
+
+STATIC void
+S_put_byte(pTHX_ SV *sv, int c)
+{
+    PERL_ARGS_ASSERT_PUT_BYTE;
+
+    if (!isPRINT(c)) {
+        switch (c) {
+            case '\r': Perl_sv_catpvf(aTHX_ sv, "\\r"); break;
+            case '\n': Perl_sv_catpvf(aTHX_ sv, "\\n"); break;
+            case '\t': Perl_sv_catpvf(aTHX_ sv, "\\t"); break;
+            case '\f': Perl_sv_catpvf(aTHX_ sv, "\\f"); break;
+            case '\a': Perl_sv_catpvf(aTHX_ sv, "\\a"); break;
+
+            default:
+                Perl_sv_catpvf(aTHX_ sv, "\\x{%x}", c);
+                break;
+        }
+    }
+    else {
+       const char string = c;
+       if (c == '-' || c == ']' || c == '\\' || c == '^')
+           sv_catpvs(sv, "\\");
+       sv_catpvn(sv, &string, 1);
+    }
+}
+
+STATIC void
+S_put_range(pTHX_ SV *sv, UV start, UV end)
+{
+
+    /* Appends to 'sv' a displayable version of the range of code points from
+     * 'start' to 'end' */
+
+    assert(start <= end);
+
+    PERL_ARGS_ASSERT_PUT_RANGE;
+
+    if (end - start < 3) {  /* Individual chars in short ranges */
+        for (; start <= end; start++)
+            put_byte(sv, start);
+    }
+    else if (   end > 255
+             || ! isALPHANUMERIC(start)
+             || ! isALPHANUMERIC(end)
+             || isDIGIT(start) != isDIGIT(end)
+             || isUPPER(start) != isUPPER(end)
+             || isLOWER(start) != isLOWER(end)
+
+                /* This final test should get optimized out except on EBCDIC
+                 * platforms, where it causes ranges that cross discontinuities
+                 * like i/j to be shown as hex instead of the misleading,
+                 * e.g. H-K (since that range includes more than H, I, J, K).
+                 * */
+             || (end - start) != NATIVE_TO_ASCII(end) - NATIVE_TO_ASCII(start))
+    {
+        Perl_sv_catpvf(aTHX_ sv, "\\x{%02" UVXf "}-\\x{%02" UVXf "}",
+                       start,
+                       (end < 256) ? end : 255);
+    }
+    else { /* Here, the ends of the range are both digits, or both uppercase,
+              or both lowercase; and there's no discontinuity in the range
+              (which could happen on EBCDIC platforms) */
+        put_byte(sv, start);
+        sv_catpvs(sv, "-");
+        put_byte(sv, end);
+    }
+}
+
+STATIC bool
+S_put_latin1_charclass_innards(pTHX_ SV *sv, char *bitmap)
+{
+    /* Appends to 'sv' a displayable version of the innards of the bracketed
+     * character class whose bitmap is 'bitmap';  Returns 'TRUE' if it actually
+     * output anything */
+
+    int i;
+    bool has_output_anything = FALSE;
+
+    PERL_ARGS_ASSERT_PUT_LATIN1_CHARCLASS_INNARDS;
+
+    for (i = 0; i < 256; i++) {
+        if (BITMAP_TEST((U8 *) bitmap,i)) {
+
+            /* The character at index i should be output.  Find the next
+             * character that should NOT be output */
+            int j;
+            for (j = i + 1; j < 256; j++) {
+                if (! BITMAP_TEST((U8 *) bitmap, j)) {
+                    break;
+                }
+            }
+
+            /* Everything between them is a single range that should be output
+             * */
+            put_range(sv, i, j - 1);
+            has_output_anything = TRUE;
+            i = j;
+        }
+    }
+
+    return has_output_anything;
+}
+
+#define CLEAR_OPTSTART \
+    if (optstart) STMT_START {                                               \
+        DEBUG_OPTIMISE_r(PerlIO_printf(Perl_debug_log,                       \
+                              " (%"IVdf" nodes)\n", (IV)(node - optstart))); \
+       optstart=NULL;                                                       \
+    } STMT_END
+
+#define DUMPUNTIL(b,e)                                                       \
+                    CLEAR_OPTSTART;                                          \
+                    node=dumpuntil(r,start,(b),(e),last,sv,indent+1,depth+1);
+
+STATIC const regnode *
+S_dumpuntil(pTHX_ const regexp *r, const regnode *start, const regnode *node,
+           const regnode *last, const regnode *plast,
+           SV* sv, I32 indent, U32 depth)
+{
+    dVAR;
+    U8 op = PSEUDO;    /* Arbitrary non-END op. */
+    const regnode *next;
+    const regnode *optstart= NULL;
+
+    RXi_GET_DECL(r,ri);
+    GET_RE_DEBUG_FLAGS_DECL;
+
+    PERL_ARGS_ASSERT_DUMPUNTIL;
+
+#ifdef DEBUG_DUMPUNTIL
+    PerlIO_printf(Perl_debug_log, "--- %d : %d - %d - %d\n",indent,node-start,
+        last ? last-start : 0,plast ? plast-start : 0);
+#endif
+
+    if (plast && plast < last)
+        last= plast;
+
+    while (PL_regkind[op] != END && (!last || node < last)) {
+       /* While that wasn't END last time... */
+       NODE_ALIGN(node);
+       op = OP(node);
+       if (op == CLOSE || op == WHILEM)
+           indent--;
+       next = regnext((regnode *)node);
+
+       /* Where, what. */
+       if (OP(node) == OPTIMIZED) {
+           if (!optstart && RE_DEBUG_FLAG(RE_DEBUG_COMPILE_OPTIMISE))
+               optstart = node;
+           else
+               goto after_print;
+       } else
+           CLEAR_OPTSTART;
+
+       regprop(r, sv, node, NULL);
+       PerlIO_printf(Perl_debug_log, "%4"IVdf":%*s%s", (IV)(node - start),
+                     (int)(2*indent + 1), "", SvPVX_const(sv));
+
+        if (OP(node) != OPTIMIZED) {
+            if (next == NULL)          /* Next ptr. */
+                PerlIO_printf(Perl_debug_log, " (0)");
+            else if (PL_regkind[(U8)op] == BRANCH
+                     && PL_regkind[OP(next)] != BRANCH )
+                PerlIO_printf(Perl_debug_log, " (FAIL)");
+            else
+                PerlIO_printf(Perl_debug_log, " (%"IVdf")", (IV)(next - start));
+            (void)PerlIO_putc(Perl_debug_log, '\n');
+        }
+
+      after_print:
+       if (PL_regkind[(U8)op] == BRANCHJ) {
+           assert(next);
+           {
+                const regnode *nnode = (OP(next) == LONGJMP
+                                       ? regnext((regnode *)next)
+                                       : next);
+                if (last && nnode > last)
+                    nnode = last;
+                DUMPUNTIL(NEXTOPER(NEXTOPER(node)), nnode);
+           }
+       }
+       else if (PL_regkind[(U8)op] == BRANCH) {
+           assert(next);
+           DUMPUNTIL(NEXTOPER(node), next);
+       }
+       else if ( PL_regkind[(U8)op]  == TRIE ) {
+           const regnode *this_trie = node;
+           const char op = OP(node);
+            const U32 n = ARG(node);
+           const reg_ac_data * const ac = op>=AHOCORASICK ?
+               (reg_ac_data *)ri->data->data[n] :
+               NULL;
+           const reg_trie_data * const trie =
+               (reg_trie_data*)ri->data->data[op<AHOCORASICK ? n : ac->trie];
+#ifdef DEBUGGING
+           AV *const trie_words
+                           = MUTABLE_AV(ri->data->data[n + TRIE_WORDS_OFFSET]);
+#endif
+           const regnode *nextbranch= NULL;
+           I32 word_idx;
+            sv_setpvs(sv, "");
+           for (word_idx= 0; word_idx < (I32)trie->wordcount; word_idx++) {
+               SV ** const elem_ptr = av_fetch(trie_words,word_idx,0);
+
+                PerlIO_printf(Perl_debug_log, "%*s%s ",
+                   (int)(2*(indent+3)), "",
+                    elem_ptr
+                    ? pv_pretty(sv, SvPV_nolen_const(*elem_ptr),
+                                SvCUR(*elem_ptr), 60,
+                                PL_colors[0], PL_colors[1],
+                                (SvUTF8(*elem_ptr)
+                                 ? PERL_PV_ESCAPE_UNI
+                                 : 0)
+                                | PERL_PV_PRETTY_ELLIPSES
+                                | PERL_PV_PRETTY_LTGT
+                            )
+                    : "???"
+                );
+                if (trie->jump) {
+                    U16 dist= trie->jump[word_idx+1];
+                   PerlIO_printf(Perl_debug_log, "(%"UVuf")\n",
+                               (UV)((dist ? this_trie + dist : next) - start));
+                    if (dist) {
+                        if (!nextbranch)
+                            nextbranch= this_trie + trie->jump[0];
+                       DUMPUNTIL(this_trie + dist, nextbranch);
+                    }
+                    if (nextbranch && PL_regkind[OP(nextbranch)]==BRANCH)
+                        nextbranch= regnext((regnode *)nextbranch);
+                } else {
+                    PerlIO_printf(Perl_debug_log, "\n");
+               }
+           }
+           if (last && next > last)
+               node= last;
+           else
+               node= next;
+       }
+       else if ( op == CURLY ) {   /* "next" might be very big: optimizer */
+           DUMPUNTIL(NEXTOPER(node) + EXTRA_STEP_2ARGS,
+                    NEXTOPER(node) + EXTRA_STEP_2ARGS + 1);
+       }
+       else if (PL_regkind[(U8)op] == CURLY && op != CURLYX) {
+           assert(next);
+           DUMPUNTIL(NEXTOPER(node) + EXTRA_STEP_2ARGS, next);
+       }
+       else if ( op == PLUS || op == STAR) {
+           DUMPUNTIL(NEXTOPER(node), NEXTOPER(node) + 1);
+       }
+       else if (PL_regkind[(U8)op] == ANYOF) {
+           /* arglen 1 + class block */
+           node += 1 + ((ANYOF_FLAGS(node) & ANYOF_POSIXL)
+                          ? ANYOF_POSIXL_SKIP
+                          : ANYOF_SKIP);
+           node = NEXTOPER(node);
+       }
+       else if (PL_regkind[(U8)op] == EXACT) {
+            /* Literal string, where present. */
+           node += NODE_SZ_STR(node) - 1;
+           node = NEXTOPER(node);
+       }
+       else {
+           node = NEXTOPER(node);
+           node += regarglen[(U8)op];
+       }
+       if (op == CURLYX || op == OPEN)
+           indent++;
+    }
+    CLEAR_OPTSTART;
+#ifdef DEBUG_DUMPUNTIL
+    PerlIO_printf(Perl_debug_log, "--- %d\n", (int)indent);
+#endif
+    return node;
+}
+
+#endif /* DEBUGGING */
+
+/*
+ * Local variables:
+ * c-indentation-style: bsd
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ *
+ * ex: set ts=8 sts=4 sw=4 et:
+ */