Perlよく知らないのでどなたか添削よろ

sub tarai
{
my ($x, $y, $z) = @_;

if ($x <= $y) {
return $y;
}
else {
return tarai(tarai($x-1, $y, $z),
tarai($y-1, $z, $x),
tarai($z-1, $x, $y));
}
}

print tarai(12, 6, 0);