#!perl

use strict;
use warnings;

use bigint;

my  $value;

my $m;
my $n;

if($#ARGV >= 1){
	$m = shift(@ARGV);
	$n = shift(@ARGV);
	}
elsif($#ARGV == 0){
	$m = shift(@ARGV);
	$n = 0;
	}
else{
	$m = 0;
	$n = 0;
	}

$value = ackermann($m, $n);

print "ackermann( $m, $n ) is $value\n";

sub ackermann {

	(my $m, my $n) = @_;

	if($m == 0){
		return $n+1;
	}
	elsif($m > 0 and $n == 0) {
		return ackermann($m - 1, 1);
	}
	elsif($m > 00 && $n > 0){
		return ackermann($m-1, ackermann($m, $n-1));
	}
}