1use integer;
2
3sub Ack {
4    return $_[0] ? ($_[1] ? Ack($_[0]-1, Ack($_[0], $_[1]-1))
5		    : Ack($_[0]-1, 1))
6	: $_[1]+1;
7}
8
9my $NUM = 9;
10$NUM = 1 if ($NUM < 1);
11my $ack = Ack(3, $NUM);
12