Woah!

That works. I expected it would fail because the first group would match everything and then there would be nothing for the 2nd group to match against.

Here's the code I used to test:

#! /usr/bin/perl -w -T

use strict;

my $str = 'foo_bar_foo_bar_12345';

print "$str\n";
$str =~ /(.*)(\1.*)/ || die "Failed!\n";
print "$2\n";
[download]

Can anyone explaine why that is?