I am also not sure what you exactly want to achieve by your second question, however try this: 
#! /usr/bin/perl

use strict;
use warnings;
use Regexp::Assemble;

my @urls = qw(
  http://www.youtube.com/user/test1
  http://www.youtube.com/user/test2
  http://www.youtube.com/user/test3
  http://www.youtube.com/user/test4
  http://www.youtube.com/user/test5 );
my $r = Regexp::Assemble->new;

for (@urls) {
  $r->add( quotemeta );
}

print $r->re, $/;

__END__

[download]
output: (?-xism:http:\/\/www\.youtube\.com\/user\/test[12345])

And you may also find valuable the String-Approx distribution from CPAN which implements approximate string matching based on Levenshtein distance.

Hope this helps.

In reply to Re: Reverse regexp a regexp? by rubasov
in thread Reverse regexp a regexp? by freakingwildchild

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