use strict;

print ackermann(3,3);

sub ackermann {
  my ($left,$right) = @_;
  print "$left,$right\n";
  if ($left == 0) {
    return $right+1
  } elsif ($right == 0) {
    return ackermann($left-1, 1)
  } else {
    return ackermann($left-1, ackermann($left, $right-1))
  };
};