#!/usr/bin/perl 
use warnings;
use strict;
use Carp;

# useless program written just to demonstrate the confess function
# Ivan Novick, May 19, 2009

my $last = 0;
for my $i (1..100){
	$last = calculate($i, $last);
}
print "$last\n";

sub calculate{
	my $one = shift;
	my $two = shift;

	my $sum1 = add($one, $one);
	my $sum2 = add($two, $two);

	return add($sum1, $sum2);
}

sub add{
	my $one = shift;
	my $two = shift;

	# this function will die and print an error message as well as a stack trace
	confess("numbers are too high") if ($two > 1000);

	return $one + $two;
}