NAME
Regexp::Compare - partial ordering for regular expressions
SYNOPSIS
use Regexp::Compare qw(is_less_or_equal);
if (is_less_or_equal($rx[i], $rx[j])) {
print "duplicate: $rx[i]\n";
}DESCRIPTION
This module implements a function comparing regular expressions: it returns true if all strings matched by the first regexp are also matched by the second. It's meant to be used for optimization of blacklists implemented by regular expressions (like, for example, http://www.communitywiki.org/cw/BannedContent ).
Both arguments of is_less_or_equal are strings - IOW the call
$rv = is_less_or_equal($rx, /hardcoded/i);probably won't do what you want - use
$rv = is_less_or_equal($rx, '(?i:hardcoded)');instead.
False return value does not imply that there's a string matched by the first regexp which isn't matched by the second - many regular expressions (i.e. those containing Perl code) are impossible to compare, and this module doesn't even implement all possible comparisons.
BUGS
EBCDIC-based platforms not supported
comparison of character classes is simplified and probably has some incorrect corner cases
comparison fails for locale-specific constructs
comparison fails for regexps with backreferences
global variables affecting regexp matching are ignored
function may die for unusual (legal but unexpected) regexp constructs
AUTHOR
Vaclav Barta, <vbarta@mangrove.cz>
COPYRIGHT AND LICENSE
Copyright (C) 2006 - 2021 by Vaclav Barta
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.30.0 or, at your option, any later version of Perl 5 you may have available.