+};
+
+my $insert_dot_at = sub {
+ my ($v, $pos, $all) = @_;
+
+ my ($int, $frac) = split /\./, $v, 2;
+ return $v unless defined $frac;
+
+ my @p;
+ push @p, $-[0] while $frac =~ /[0-9]/g;
+ my %digit = map { $_ => 1 } @p;
+
+ my $shift = 0;
+ for (my $i = $pos; $i < @p; $i += $pos) {
+ if ($digit{$i}) {
+ substr($frac, $i + $shift, 0) = '.';
+ ++$shift;
+ }
+ last unless $all;
+ }
+
+ "$int.$frac";
+};
+
+my $insert_dot_at_1 = sub { $insert_dot_at->($_[0], 1, 0) },
+my $insert_dot_at_all_1 = sub { $insert_dot_at->($_[0], 1, 1) },
+my $insert_dot_at_2 = sub { $insert_dot_at->($_[0], 2, 0) },
+my $insert_dot_at_all_2 = sub { $insert_dot_at->($_[0], 2, 1) },
+my $insert_dot_at_all_3 = sub { $insert_dot_at->($_[0], 3, 1) },
+
+my $pad_decimals_to = sub {
+ my ($v, $n) = @_;
+
+ my ($int, $frac) = split /\./, $v, 2;
+ return $v unless defined $v;
+
+ my $l = length $frac;
+ if ($l < $n) {
+ $frac .= '0' x ($n - $l);
+ }
+
+ "$int.$frac";
+};
+
+my $pad_decimals_to_2 = sub { $pad_decimals_to->($_[0], 2) };
+my $pad_decimals_to_4 = sub { $pad_decimals_to->($_[0], 4) };
+
+my $correct_suffixes = sub {
+ my ($v) = @_;
+
+ $v = $default_mapping->($v);
+ $v =~ s/(?<!_)((?:alpha|beta|pre|rc|p)\d*)\b/_$1/g;
+
+ return $v;
+};
+
+my $strip_letters = sub {
+ my ($v) = @_;
+
+ $v = $default_mapping->($v);
+ $v =~ s/(?<=\d)[a-z]+//g;
+
+ return $v;
+};
+
+my $letters_as_suffix = sub {
+ my ($v) = @_;
+
+ $v = $default_mapping->($v);
+ $v =~ s/(?<=\d)b(?=\d)/_beta/g;
+
+ return $v;
+};
+
+my %version_mismatch;
+
+$version_mismatch{$_} = $insert_dot_at_1 for qw/
+ CGI-Simple
+/;
+
+$version_mismatch{$_} = $insert_dot_at_all_1 for qw/
+ AnyEvent
+ Archive-Rar
+ IO-AIO
+ Image-Size
+ Linux-Inotify2
+ PadWalker
+ Tie-Array-Sorted
+ Tk-TableMatrix
+ XML-RSS-Feed
+/;
+
+$version_mismatch{$_} = $insert_dot_at_2 for qw/
+ Error
+/;
+
+$version_mismatch{$_} = $insert_dot_at_all_2 for qw/
+ Authen-Htpasswd
+ BSD-Resource
+ CDDB
+ Cairo
+ Curses-UI
+ DBD-mysql
+ Email-MessageID
+ ExtUtils-CBuilder
+ ExtUtils-ParseXS
+ FileHandle-Unget
+ FreezeThaw
+ Lexical-Persistence
+ Lingua-EN-Inflect
+ Mail-Mbox-MessageParser
+ Module-Build
+ SQL-Abstract-Limit
+ Term-ReadLine-Perl
+ Test-Differences
+ Time-HiRes
+ Time-Local
+ perl-ldap
+/;
+
+$version_mismatch{$_} = $insert_dot_at_all_3 for qw/
+ Parse-RecDescent
+ Return-Value
+/;
+
+$version_mismatch{$_} = $pad_decimals_to_2 for qw/
+ Nmap-Parser
+ XML-AutoWriter
+/;
+
+$version_mismatch{$_} = $pad_decimals_to_4 for qw/
+ Convert-BER
+/;
+
+$version_mismatch{$_} = $correct_suffixes for qw/
+ Gimp
+ XML-Grove
+/;
+
+$version_mismatch{$_} = $strip_letters for qw/
+ DelimMatch
+ SGMLSpm
+/;
+
+$version_mismatch{$_} = $letters_as_suffix for qw/
+ Frontier-RPC
+/;
+
+sub version_c2g {
+ my ($n, $v) = @_;
+
+ return unless defined $v;
+
+ my $handler;
+ $handler = $version_mismatch{$n} if defined $n;
+ $handler = $default_mapping unless defined $handler;
+
+ return $handler->($v);
+}
+
+=head2 C<perl_version_c2g $version>
+
+Converts a perl version as you can find it in prerequisites to a Gentoo version number.
+
+=cut
+
+sub perl_version_c2g {
+ my ($v) = @_;
+
+ return unless defined $v and $v =~ /^[0-9\.]+$/;
+
+ my @parts;
+ if (my ($version, $subversion) = $v =~ /^([0-9]+)\.(0[^\.]+)$/) {
+ my $len = length $subversion;
+ if (my $pad = $len % 3) {
+ $subversion .= '0' x (3 - $pad);
+ }
+ @parts = ($version, $subversion =~ /(.{1,3})/g);
+ } else {
+ @parts = split /\./, $v;
+ }
+
+ return join '.', map int, @parts;