sub lcss
{
    my $strings = join "\0", @_;
    my $lcs;

    for my $n (1 .. length $strings)
    {
        my $re = "(.{$n})" . '.*\0.*\1' x (@_ - 1);
        last unless $strings =~ $re;
        $lcs = $1;
    }

    return $lcs;
}