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package Devel::FindRef; |
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|
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use strict; |
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|
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use XSLoader; |
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use Scalar::Util; |
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|
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BEGIN { |
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our $VERSION = '1.2'; |
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XSLoader::load __PACKAGE__, $VERSION; |
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} |
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|
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=head1 NAME |
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|
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Devel::FindRef - where is that reference to my scalar hiding? |
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|
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=head1 SYNOPSIS |
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|
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use Devel::FindRef; |
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|
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=head1 DESCRIPTION |
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|
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Tracking down reference problems (e.g. you expect some object to be |
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destroyed, but there are still references to it that keep it alive) can be |
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very hard. Fortunately, perl keeps track of all its values, so tracking |
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references "backwards" is usually possible. |
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|
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The C<track> function can help track down some of those references back to |
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the variables containing them. |
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|
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For example, for this fragment: |
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|
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package Test; |
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|
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our $var = "hi\n"; |
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my $x = \$var; |
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our %hash = (ukukey => \$var); |
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our $hash2 = {ukukey2 => \$var}; |
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|
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sub testsub { |
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my $local = $hash2; |
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print Devel::FindRef::track \$var; |
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} |
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|
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testsub; |
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|
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The output is as follows (or similar to this, in case I forget to update |
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the manpage after some changes): |
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|
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SCALAR(0x7bd2d0) is |
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in the global $Test::var. |
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referenced by REF(0x7bd240), which is |
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in the member 'ukukey2' of HASH(0x7bd228), which is |
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referenced by REF(0x81dae8), which is |
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in the lexical '$local' in CODE(0x81da88), which is |
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in the global &Test::testsub. |
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referenced by REF(0x81da40), which is |
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in the global $Test::hash2. |
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referenced by REF(0x79f3f8), which is |
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in the lexical '$x' in CODE(0x79f518), which is |
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the containing scope for CODE(0x81da88), which is |
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in the global &Test::testsub. |
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referenced by REF(0x79f2f0), which is |
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not found anywhere I looked :( |
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referenced by REF(0x79f140), which is |
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in the member 'ukukey' of HASH(0x81d698), which is |
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in the global %Test::hash. |
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|
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It is a bit convoluted to read, but basically it says that the value |
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stored in C<$var> can be found: |
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|
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=over 4 |
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|
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=item - in some variable C<$x> whose origin is not known (I frankly have no |
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idea why, hints accepted). |
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|
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=item - in the hash element with key C<ukukey> in the hash stored in C<%Test::hash>. |
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|
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=item - in the global variable named C<$Test::var>. |
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|
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=item - in the hash element C<ukukey2>, in the hash in the my variable |
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C<$local> in the sub C<Test::testsub> and also in the hash referenced by |
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C<$Test::hash2>. |
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|
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=back |
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|
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=head1 EXPORTS |
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|
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None. |
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|
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=head1 FUNCTIONS |
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|
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=over 4 |
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|
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=item $string = Devel::FindRef::track $ref[, $depth] |
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|
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Track the perl value pointed to by C<$ref> up to a depth of C<$depth> and |
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return a descriptive string. C<$ref> can point at any perl value, be it |
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anonymous sub, hash, array, scalar etc. |
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|
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This is the function you most often use. |
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|
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=cut |
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|
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sub find($); |
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|
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sub track { |
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my ($ref, $depth) = @_; |
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@_ = (); |
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|
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my $buf = ""; |
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my %seen; |
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|
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Scalar::Util::weaken $ref; |
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|
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my $track; $track = sub { |
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my ($refref, $depth, $indent) = @_; |
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|
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if ($depth) { |
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my (@about) = find $$refref; |
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if (@about) { |
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for my $about (@about) { |
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$buf .= "$indent" . (@about > 1 ? "+- " : " ") . $about->[0]; |
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if (@$about > 1) { |
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if ($seen{$about->[1]+0}++) { |
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$buf .= " $about->[1], which was seen before.\n"; |
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} else { |
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$buf .= " $about->[1], which is\n"; |
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$track->(\$about->[1], $depth - 1, $about == $about[-1] ? "$indent " : "$indent| "); |
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} |
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} else { |
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$buf .= ".\n"; |
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} |
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} |
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} else { |
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$buf .= "$indent not found anywhere I looked :(\n"; |
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} |
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} else { |
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$buf .= "$indent not referenced within the search depth.\n"; |
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} |
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}; |
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|
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$buf .= "$ref is\n"; |
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$track->(\$ref, $depth || $ENV{PERL_DEVEL_FINDREF_DEPTH} || 10, ""); |
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$buf |
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} |
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|
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=item @references = Devel::FindRef::find $ref |
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|
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Return arrayrefs that contain [$message, $ref] pairs. The message |
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describes what kind of reference was found and the C<$ref> is the |
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reference itself, which can be omitted if C<find> decided to end the |
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search. The returned references are all weak references. |
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|
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The C<track> function uses this to find references to the value you are |
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interested in and recurses on the returned references. |
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|
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=cut |
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|
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sub find($) { |
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my ($about, $excl) = &find_; |
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my %excl = map +($_ => undef), @$excl; |
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grep !exists $excl{$_->[1] + 0}, @$about |
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} |
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|
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=item $ref = Devel::FindRef::ptr2ref $integer |
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|
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Sometimes you know (from debugging output) the address of a perl scalar |
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you are interested in (e.g. C<HASH(0x176ff70)>). This function can be used |
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to turn the address into a reference to that scalar. It is quite safe to |
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call on valid addresses, but extremely dangerous to call on invalid ones. |
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|
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# we know that HASH(0x176ff70) exists, so turn it into a hashref: |
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my $ref_to_hash = Devel::FindRef::ptr2ref 0x176ff70; |
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|
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=back |
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|
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=head1 ENVIRONMENT VARIABLES |
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|
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You can set the environment variable C<PERL_DEVEL_FINDREF_DEPTH> to an |
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integer to override the default depth in C<track>. If a call explicitly |
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specified a depth it is not overridden. |
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|
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=head1 AUTHOR |
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|
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Marc Lehmann <pcg@goof.com>. |
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|
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=head1 BUGS |
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|
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Only code values, arrays, hashes, scalars and magic are being looked at. |
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|
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This is a quick hack only. |
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|
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=head1 COPYRIGHT AND LICENSE |
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|
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Copyright (C) 2007 by Marc Lehmann. |
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|
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This library is free software; you can redistribute it and/or modify |
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it under the same terms as Perl itself, either Perl version 5.8.8 or, |
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at your option, any later version of Perl 5 you may have available. |
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|
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=cut |
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|
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