Mine

use IO::Socket;

$num = 1;
while($num != 10000) {
        my $sock = new IO::Socket::INET (
                PeerAddr => 'localhost',
                PeerPort => $num,
                Proto => 'tcp',
        );
        if ($sock) {
                print $num, "\n";
        }
        $num = $num + 1;
}