in reply to Finding largest common subset in lists?

The magic is in the module Algorithm::Diff, which implements the Largest Common Subsequence (LCS), which is a more accurate name of the problem you describe (a set has no order).

perl -MHTTP::Daemon -MHTTP::Response -MLWP::Simple -e ' ; # The $d = new HTTP::Daemon and fork and getprint $d->url and exit;#spider ($c = $d->accept())->get_request(); $c->send_response( new #in the HTTP::Response(200,$_,$_,qq(Just another Perl hacker\n))); ' # web