#!/usr/bin/perl -w

use strict;

use v5.10;

sub swap {

$_[0] = $_[0] + $_[1];

$_[1] = $_[0] - $_[1];

$_[0] = $_[0] - $_[1];

}

my $a = 0;

my $b = 1;

while ($b < $ARGV[0]) {

$a += $b;

say $b;

swap($a, $b);

}