X-Git-Url: http://git.vpit.fr/?p=perl%2Fmodules%2FScope-Upper.git;a=blobdiff_plain;f=README;h=15bb1ec4605ba4544036305244a377a8aa8cc345;hp=499ba67abc7184f6ca249508eb9283ba139fa0bc;hb=HEAD;hpb=c8549c2d49ee305498c19318c51dc6540dba8b3f diff --git a/README b/README index 499ba67..1f7b09e 100644 --- a/README +++ b/README @@ -2,59 +2,187 @@ NAME Scope::Upper - Act on upper scopes. VERSION - Version 0.03 + Version 0.34 SYNOPSIS - package X; + "reap", "localize", "localize_elem", "localize_delete" and "WORDS" : - use Scope::Upper qw/reap localize localize_elem localize_delete/; + package Scope; - sub desc { shift->{desc} } + use Scope::Upper qw< + reap localize localize_elem localize_delete + :words + >; - sub set_tag { - my ($desc) = @_; + sub new { + my ($class, $name) = @_; - # First localize $x so that it gets destroyed last - localize '$x' => bless({ desc => $desc }, __PACKAGE__) => 1; + localize '$tag' => bless({ name => $name }, $class) => UP; - reap sub { - my $pkg = caller; - my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope - print $x->desc . ": done\n"; - } => 1; + reap { print Scope->tag->name, ": end\n" } UP; + } + + # Get the tag stored in the caller namespace + sub tag { + my $l = 0; + my $pkg = __PACKAGE__; + $pkg = caller $l++ while $pkg eq __PACKAGE__; + + no strict 'refs'; + ${$pkg . '::tag'}; + } + + sub name { shift->{name} } + # Locally capture warnings and reprint them with the name prefixed + sub catch { localize_elem '%SIG', '__WARN__' => sub { - my $pkg = caller; - my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope - CORE::warn($x->desc . ': ' . join('', @_)); - } => 1; + print Scope->tag->name, ': ', @_; + } => UP; + } + + # Locally clear @INC + sub private { + for (reverse 0 .. $#INC) { + # First UP is the for loop, second is the sub boundary + localize_delete '@INC', $_ => UP UP; + } + } + + ... + + package UserLand; + + { + Scope->new("top"); # initializes $UserLand::tag + + { + Scope->catch; + my $one = 1 + undef; # prints "top: Use of uninitialized value..." + + { + Scope->private; + eval { require Cwd }; + print $@; # prints "Can't locate Cwd.pm in @INC + } # (@INC contains:) at..." + + require Cwd; # loads Cwd.pm + } + + } # prints "top: done" + + "unwind" and "want_at" : - localize_delete '@ARGV', $#ARGV => 1; # delete last @ARGV element + package Try; + + use Scope::Upper qw; + + sub try (&) { + my @result = shift->(); + my $cx = SUB UP; # Point to the sub above this one + unwind +(want_at($cx) ? @result : scalar @result) => $cx; + } + + ... + + sub zap { + try { + my @things = qw; + return @things; # returns to try() and then outside zap() + # not reached + }; + # not reached + } + + my @stuff = zap(); # @stuff contains qw + my $stuff = zap(); # $stuff contains 3 + + "uplevel" : + + package Uplevel; + + use Scope::Upper qw; + + sub target { + faker(@_); + } + + sub faker { + uplevel { + my $sub = (caller 0)[3]; + print "$_[0] from $sub()"; + } @_ => CALLER(1); } - package Y; + target('hello'); # "hello from Uplevel::target()" + + "uid" and "validate_uid" : + + use Scope::Upper qw; + + my $uid; { - X::set_tag('pie'); - # $x is now a X object, and @ARGV has one element less - warn 'what'; # warns "pie: what at ..." + $uid = uid(); + { + if ($uid eq uid(UP)) { # yes + ... + } + if (validate_uid($uid)) { # yes + ... + } + } + } + + if (validate_uid($uid)) { # no ... - } # "pie: done" is printed + } DESCRIPTION - This module lets you defer actions that will take place when the control - flow returns into an upper scope. Currently, you can hook an upper scope - end, or localize variables, array/hash values or deletions of elements - in higher contexts. + This module lets you defer actions *at run-time* that will take place + when the control flow returns into an upper scope. Currently, you can: + + * hook an upper scope end with "reap" ; + + * localize variables, array/hash values or deletions of elements in + higher contexts with respectively "localize", "localize_elem" and + "localize_delete" ; + + * return values immediately to an upper level with "unwind", "yield" + and "leave" ; + + * gather information about an upper context with "want_at" and + "context_info" ; + + * execute a subroutine in the setting of an upper subroutine stack + frame with "uplevel" ; + + * uniquely identify contexts with "uid" and "validate_uid". FUNCTIONS - "reap $callback, $level" - Add a destructor that calls $callback when the $level-th upper scope - ends, where 0 corresponds to the current scope. + In all those functions, $context refers to the target scope. + + You have to use one or a combination of "WORDS" to build the $context + passed to these functions. This is needed in order to ensure that the + module still works when your program is ran in the debugger. The only + thing you can assume is that it is an *absolute* indicator of the frame, + which means that you can safely store it at some point and use it when + needed, and it will still denote the original scope. - "localize $what, $value, $level" - A "local" delayed to the time of first return into the $level-th upper - scope. $what can be : + "reap" + reap { ... }; + reap { ... } $context; + &reap($callback, $context); + + Adds a destructor that calls $callback (in void context) when the upper + scope represented by $context ends. + + "localize" + localize $what, $value; + localize $what, $value, $context; + + Introduces a "local" delayed to the time of first return into the upper + scope denoted by $context. $what can be : * A glob, in which case $value can either be a glob or a reference. "localize" follows then the same syntax as "local *x = $value". For @@ -67,56 +195,532 @@ FUNCTIONS syntax as "local $x = $value", i.e. $value isn't dereferenced. For example, - localize '$x', \'foo' => 0; + localize '$x', \'foo' => HERE; will set $x to a reference to the string 'foo'. Other sigils ('@', '%', '&' and '*') require $value to be a reference of the corresponding type. When the symbol is given by a string, it is resolved when the actual - localization takes place and not when "localize" is called. This - means that - - sub tag { localize '$x', $_[0] => 1; } - - will localize in the caller's namespace. - - "localize_elem $what, $key, $value, $level" - Similar to "localize" but for array and hash elements. If $what is a - glob, the slot to fill is determined from which type of reference $value - is ; otherwise it's inferred from the sigil. $key is either an array - index or a hash key, depending of which kind of variable you localize. - - "localize_delete $what, $key, $level" - Similiar to "localize", but for deleting variables or array/hash - elements. $what can be: + localization takes place and not when "localize" is called. Thus, if + the symbol name is not qualified, it will refer to the variable in + the package where the localization actually takes place and not in + the one where the "localize" call was compiled. For example, + + { + package Scope; + sub new { localize '$tag', $_[0] => UP } + } + + { + package Tool; + { + Scope->new; + ... + } + } + + will localize $Tool::tag and not $Scope::tag. If you want the other + behaviour, you just have to specify $what as a glob or a qualified + name. + + Note that if $what is a string denoting a variable that wasn't + declared beforehand, the relevant slot will be vivified as needed + and won't be deleted from the glob when the localization ends. This + situation never arises with "local" because it only compiles when + the localized variable is already declared. Although I believe it + shouldn't be a problem as glob slots definedness is pretty much an + implementation detail, this behaviour may change in the future if + proved harmful. + + "localize_elem" + localize_elem $what, $key, $value; + localize_elem $what, $key, $value, $context; + + Introduces a "local $what[$key] = $value" or "local $what{$key} = + $value" delayed to the time of first return into the upper scope denoted + by $context. Unlike "localize", $what must be a string and the type of + localization is inferred from its sigil. The two only valid types are + array and hash ; for anything besides those, "localize_elem" will throw + an exception. $key is either an array index or a hash key, depending of + which kind of variable you localize. + + If $what is a string pointing to an undeclared variable, the variable + will be vivified as soon as the localization occurs and emptied when it + ends, although it will still exist in its glob. + + "localize_delete" + localize_delete $what, $key; + localize_delete $what, $key, $context; + + Introduces the deletion of a variable or an array/hash element delayed + to the time of first return into the upper scope denoted by $context. + $what can be: * A glob, in which case $key is ignored and the call is equivalent to "local *x". * A string beginning with '@' or '%', for which the call is equivalent - to respectiveley "local $a[$key]; delete $a[$key]" and "local + to respectively "local $a[$key]; delete $a[$key]" and "local $h{$key}; delete $h{$key}". * A string beginning with '&', which more or less does "undef &func" in the upper scope. It's actually more powerful, as &func won't even "exists" anymore. $key is ignored. - "TOPLEVEL" - Returns the level that currently represents the highest scope. + "unwind" + unwind; + unwind @values, $context; + + Returns @values *from* the subroutine, eval or format context pointed by + or just above $context, and immediately restarts the program flow at + this point - thus effectively returning @values to an upper scope. If + @values is empty, then the $context parameter is optional and defaults + to the current context (making the call equivalent to a bare "return;") + ; otherwise it is mandatory. + + The upper context isn't coerced onto @values, which is hence always + evaluated in list context. This means that + + my $num = sub { + my @a = ('a' .. 'z'); + unwind @a => HERE; + # not reached + }->(); + + will set $num to 'z'. You can use "want_at" to handle these cases. + + "yield" + yield; + yield @values, $context; + + Returns @values *from* the context pointed by or just above $context, + and immediately restarts the program flow at this point. If @values is + empty, then the $context parameter is optional and defaults to the + current context ; otherwise it is mandatory. + + "yield" differs from "unwind" in that it can target *any* upper scope + (besides a "s///e" substitution context) and not necessarily a sub, an + eval or a format. Hence you can use it to return values from a "do" or a + "map" block : + + my $now = do { + local $@; + eval { require Time::HiRes } or yield time() => HERE; + Time::HiRes::time(); + }; + + my @uniq = map { + yield if $seen{$_}++; # returns the empty list from the block + ... + } @things; + + Like for "unwind", the upper context isn't coerced onto @values. You can + use the fifth value returned by "context_info" to handle context + coercion. + + "leave" + leave; + leave @values; + + Immediately returns @values from the current block, whatever it may be + (besides a "s///e" substitution context). "leave" is actually a synonym + for "yield HERE", while "leave @values" is a synonym for "yield @values, + HERE". + + Like for "yield", you can use the fifth value returned by "context_info" + to handle context coercion. + + "want_at" + my $want = want_at; + my $want = want_at $context; + + Like "wantarray" in perlfunc, but for the subroutine, eval or format + context located at or just above $context. + + It can be used to revise the example showed in "unwind" : + + my $num = sub { + my @a = ('a' .. 'z'); + unwind +(want_at(HERE) ? @a : scalar @a) => HERE; + # not reached + }->(); + + will rightfully set $num to 26. + + "context_info" + my ($package, $filename, $line, $subroutine, $hasargs, + $wantarray, $evaltext, $is_require, $hints, $bitmask, + $hinthash) = context_info $context; + + Gives information about the context denoted by $context, akin to what + "caller" in perlfunc provides but not limited only to subroutine, eval + and format contexts. When $context is omitted, it defaults to the + current context. + + The returned values are, in order : + + * *(index 0)* : the namespace in use when the context was created ; + + * *(index 1)* : the name of the file at the point where the context + was created ; + + * *(index 2)* : the line number at the point where the context was + created ; + + * *(index 3)* : the name of the subroutine called for this context, or + "undef" if this is not a subroutine context ; + + * *(index 4)* : a boolean indicating whether a new instance of @_ was + set up for this context, or "undef" if this is not a subroutine + context ; + + * *(index 5)* : the context (in the sense of "wantarray" in perlfunc) + in which the context (in our sense) is executed ; + + * *(index 6)* : the contents of the string being compiled for this + context, or "undef" if this is not an eval context ; + + * *(index 7)* : a boolean indicating whether this eval context was + created by "require", or "undef" if this is not an eval context ; + + * *(index 8)* : the value of the lexical hints in use when the context + was created ; + + * *(index 9)* : a bit string representing the warnings in use when the + context was created ; + + * *(index 10)* : a reference to the lexical hints hash in use when the + context was created (only on perl 5.10 or greater). + + "uplevel" + my @ret = uplevel { ...; return @ret }; + my @ret = uplevel { my @args = @_; ...; return @ret } @args, $context; + my @ret = &uplevel($callback, @args, $context); + + Executes the code reference $callback with arguments @args as if it were + located at the subroutine stack frame pointed by $context, effectively + fooling "caller" and "die" into believing that the call actually + happened higher in the stack. The code is executed in the context of the + "uplevel" call, and what it returns is returned as-is by "uplevel". + + sub target { + faker(@_); + } + + sub faker { + uplevel { + map { 1 / $_ } @_; + } @_ => CALLER(1); + } + + my @inverses = target(1, 2, 4); # @inverses contains (0, 0.5, 0.25) + my $count = target(1, 2, 4); # $count is 3 + + Note that if @args is empty, then the $context parameter is optional and + defaults to the current context ; otherwise it is mandatory. + + Sub::Uplevel also implements a pure-Perl version of "uplevel". Both are + identical, with the following caveats : + + * The Sub::Uplevel implementation of "uplevel" may execute a code + reference in the context of any upper stack frame. The Scope::Upper + version can only uplevel to a subroutine stack frame, and will croak + if you try to target an "eval" or a format. + + * Exceptions thrown from the code called by this version of "uplevel" + will not be caught by "eval" blocks between the target frame and the + uplevel call, while they will for Sub::Uplevel's version. This means + that : + + eval { + sub { + local $@; + eval { + sub { + uplevel { die 'wut' } CALLER(2); # for Scope::Upper + # uplevel(3, sub { die 'wut' }) # for Sub::Uplevel + }->(); + }; + print "inner block: $@"; + $@ and exit; + }->(); + }; + print "outer block: $@"; + + will print "inner block: wut..." with Sub::Uplevel and "outer block: + wut..." with Scope::Upper. + + * Sub::Uplevel globally overrides the Perl keyword "caller", while + Scope::Upper does not. + + A simple wrapper lets you mimic the interface of "uplevel" in + Sub::Uplevel : + + use Scope::Upper; + + sub uplevel { + my $frame = shift; + my $code = shift; + my $cxt = Scope::Upper::CALLER($frame); + &Scope::Upper::uplevel($code => @_ => $cxt); + } + + Albeit the three exceptions listed above, it passes all the tests of + Sub::Uplevel. + + "uid" + my $uid = uid; + my $uid = uid $context; + + Returns an unique identifier (UID) for the context (or dynamic scope) + pointed by $context, or for the current context if $context is omitted. + This UID will only be valid for the life time of the context it + represents, and another UID will be generated next time the same scope + is executed. + + my $uid; + + { + $uid = uid; + if ($uid eq uid()) { # yes, this is the same context + ... + } + { + if ($uid eq uid()) { # no, we are one scope below + ... + } + if ($uid eq uid(UP)) { # yes, UP points to the same scope as $uid + ... + } + } + } + + # $uid is now invalid + + { + if ($uid eq uid()) { # no, this is another block + ... + } + } + + For example, each loop iteration gets its own UID : + + my %uids; + + for (1 .. 5) { + my $uid = uid; + $uids{$uid} = $_; + } + + # %uids has 5 entries + + The UIDs are not guaranteed to be numbers, so you must use the "eq" + operator to compare them. + + To check whether a given UID is valid, you can use the "validate_uid" + function. + + "validate_uid" + my $is_valid = validate_uid $uid; + + Returns true if and only if $uid is the UID of a currently valid context + (that is, it designates a scope that is higher than the current one in + the call stack). + + my $uid; + + { + $uid = uid(); + if (validate_uid($uid)) { # yes + ... + } + { + if (validate_uid($uid)) { # yes + ... + } + } + } + + if (validate_uid($uid)) { # no + ... + } + +CONSTANTS + "SU_THREADSAFE" + True iff the module could have been built when thread-safety features. + +WORDS + Constants + "TOP" + my $top_context = TOP; + + Returns the context that currently represents the highest scope. + + "HERE" + my $current_context = HERE; + + The context of the current scope. + + Getting a context from a context + For any of those functions, $from is expected to be a context. When + omitted, it defaults to the current context. + + "UP" + my $upper_context = UP; + my $upper_context = UP $from; + + The context of the scope just above $from. If $from points to the + top-level scope in the current stack, then a warning is emitted and + $from is returned (see "DIAGNOSTICS" for details). + + "SUB" + my $sub_context = SUB; + my $sub_context = SUB $from; + + The context of the closest subroutine above $from. If $from already + designates a subroutine context, then it is returned as-is ; hence "SUB + SUB == SUB". If no subroutine context is present in the call stack, then + a warning is emitted and the current context is returned (see + "DIAGNOSTICS" for details). + + "EVAL" + my $eval_context = EVAL; + my $eval_context = EVAL $from; + + The context of the closest eval above $from. If $from already designates + an eval context, then it is returned as-is ; hence "EVAL EVAL == EVAL". + If no eval context is present in the call stack, then a warning is + emitted and the current context is returned (see "DIAGNOSTICS" for + details). + + Getting a context from a level + Here, $level should denote a number of scopes above the current one. + When omitted, it defaults to 0 and those functions return the same + context as "HERE". + + "SCOPE" + my $context = SCOPE; + my $context = SCOPE $level; + + The $level-th upper context, regardless of its type. If $level points + above the top-level scope in the current stack, then a warning is + emitted and the top-level context is returned (see "DIAGNOSTICS" for + details). + + "CALLER" + my $context = CALLER; + my $context = CALLER $level; + + The context of the $level-th upper subroutine/eval/format. It kind of + corresponds to the context represented by "caller $level", but while + e.g. "caller 0" refers to the caller context, "CALLER 0" will refer to + the top scope in the current context. If $level points above the + top-level scope in the current stack, then a warning is emitted and the + top-level context is returned (see "DIAGNOSTICS" for details). + + Examples + Where "reap" fires depending on the $cxt : + + sub { + eval { + sub { + { + reap \&cleanup => $cxt; + ... + } # $cxt = SCOPE(0) = HERE + ... + }->(); # $cxt = SCOPE(1) = UP = SUB = CALLER(0) + ... + }; # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1) + ... + }->(); # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2) + ... + + Where "localize", "localize_elem" and "localize_delete" act depending on + the $cxt : + + sub { + eval { + sub { + { + localize '$x' => 1 => $cxt; + # $cxt = SCOPE(0) = HERE + ... + } + # $cxt = SCOPE(1) = UP = SUB = CALLER(0) + ... + }->(); + # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1) + ... + }; + # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2) + ... + }->(); + # $cxt = SCOPE(4), UP SUB UP SUB = UP SUB EVAL = UP CALLER(2) = TOP + ... + + Where "unwind", "yield", "want_at", "context_info" and "uplevel" point + to depending on the $cxt: + + sub { + eval { + sub { + { + unwind @things => $cxt; # or yield @things => $cxt + # or uplevel { ... } $cxt + ... + } + ... + }->(); # $cxt = SCOPE(0) = SCOPE(1) = HERE = UP = SUB = CALLER(0) + ... + }; # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1) (*) + ... + }->(); # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2) + ... + + # (*) Note that uplevel() will croak if you pass that scope frame, + # because it cannot target eval scopes. + +DIAGNOSTICS + "Cannot target a scope outside of the current stack" + This warning is emitted when "UP", "SCOPE" or "CALLER" end up pointing + to a context that is above the top-level context of the current stack. + It indicates that you tried to go higher than the main scope, or to + point across a "DESTROY" method, a signal handler, an overloaded or tied + method call, a "require" statement or a "sort" callback. In this case, + the resulting context is the highest reachable one. + + "No targetable %s scope in the current stack" + This warning is emitted when you ask for an "EVAL" or "SUB" context and + no such scope can be found in the call stack. The resulting context is + the current one. EXPORT - The functions "reap", "localize", "localize_elem", "localize_delete" and - "TOPLEVEL" are only exported on request, either individually or by the - tags ':funcs' and ':all'. + The functions "reap", "localize", "localize_elem", "localize_delete", + "unwind", "yield", "leave", "want_at", "context_info" and "uplevel" are + only exported on request, either individually or by the tags ':funcs' + and ':all'. + + The constant "SU_THREADSAFE" is also only exported on request, + individually or by the tags ':consts' and ':all'. + + Same goes for the words "TOP", "HERE", "UP", "SUB", "EVAL", "SCOPE" and + "CALLER" that are only exported on request, individually or by the tags + ':words' and ':all'. CAVEATS + It is not possible to act upon a scope that belongs to another perl + 'stack', i.e. to target a scope across a "DESTROY" method, a signal + handler, an overloaded or tied method call, a "require" statement or a + "sort" callback. + Be careful that local variables are restored in the reverse order in which they were localized. Consider those examples: local $x = 0; { - reap sub { print $x } => 0; + reap sub { print $x } => HERE; local $x = 1; ... } @@ -124,7 +728,7 @@ CAVEATS ... { local $x = 1; - reap sub { $x = 2 } => 0; + reap sub { $x = 2 } => HERE; ... } # $x is 0 @@ -132,19 +736,68 @@ CAVEATS The first case is "solved" by moving the "local" before the "reap", and the second by using "localize" instead of "reap". - "reap", "localize" and "localize_elem" effects can't cross "BEGIN" - blocks, hence calling those functions in "import" is deemed to be - useless. This is an hopeless case because "BEGIN" blocks are executed + The effects of "reap", "localize" and "localize_elem" can't cross + "BEGIN" blocks, hence calling those functions in "import" is deemed to + be useless. This is an hopeless case because "BEGIN" blocks are executed once while localizing constructs should do their job at each run. + However, it's possible to hook the end of the current scope compilation + with B::Hooks::EndOfScope. + + Some rare oddities may still happen when running inside the debugger. It + may help to use a perl higher than 5.8.9 or 5.10.0, as they contain some + context-related fixes. + + Calling "goto" to replace an "uplevel"'d code frame does not work : + + * for a "perl" older than the 5.8 series ; + + * for a "DEBUGGING" "perl" run with debugging flags set (as in "perl + -D ...") ; + + * when the runloop callback is replaced by another module. + + In those three cases, "uplevel" will look for a "goto &sub" statement in + its callback and, if there is one, throw an exception before executing + the code. + + Moreover, in order to handle "goto" statements properly, "uplevel" + currently has to suffer a run-time overhead proportional to the size of + the callback in every case (with a small ratio), and proportional to the + size of all the code executed as the result of the "uplevel" call + (including subroutine calls inside the callback) when a "goto" statement + is found in the "uplevel" callback. Despite this shortcoming, this XS + version of "uplevel" should still run way faster than the pure-Perl + version from Sub::Uplevel. + + Starting from "perl" 5.19.4, it is unfortunately no longer possible to + reliably throw exceptions from "uplevel"'d code while the debugger is in + use. This may be solved in a future version depending on how the core + evolves. DEPENDENCIES - XSLoader (standard since perl 5.006). + perl 5.6.1. + + A C compiler. This module may happen to build with a C++ compiler as + well, but don't rely on it, as no guarantee is made in this regard. + + XSLoader (core since perl 5.6.0). SEE ALSO + "local" in perlfunc, "Temporary Values via local()" in perlsub. + Alias, Hook::Scope, Scope::Guard, Guard. + Sub::Uplevel. + + Continuation::Escape is a thin wrapper around Scope::Upper that gives + you a continuation passing style interface to "unwind". It's easier to + use, but it requires you to have control over the scope where you want + to return. + + Scope::Escape. + AUTHOR - Vincent Pit, "", . + Vincent Pit "". You can contact me by mail or on "irc.perl.org" (vincent). @@ -160,14 +813,19 @@ SUPPORT perldoc Scope::Upper - Tests code coverage report is available at - . - ACKNOWLEDGEMENTS Inspired by Ricardo Signes. + The reimplementation of a large part of this module for perl 5.24 was + provided by David Mitchell. His work was sponsored by the Perl 5 Core + Maintenance Grant from The Perl Foundation. + + Thanks to Shawn M. Moore for motivation. + COPYRIGHT & LICENSE - Copyright 2008-2009 Vincent Pit, all rights reserved. + Copyright + 2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019,2021,2023 + Vincent Pit, all rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.