#!/usr/bin/perl

use strict;
use warnings;
my ($power, $result);

sub binomial_power 
{
	my ($c, $xp, $yp) = @_;
	$result .= $c . "x^" . $xp . "y^" . ($yp - 1) . " + ";
	if ($yp <= $power ) { binomial_power ((($c * $xp)/$yp), ($xp-1), ($yp+1));}
}

# Get the input
print "\nEnter the power: ";
chomp($power = (<STDIN>));

# Do the work
binomial_power (1, $power, 1);

# Make it pretty
$result =~ s/1x/x/g;
$result =~ s/x\^1/x/g;
$result =~ s/y\^1/y/g;
$result =~ s/x\^0//g;
$result =~ s/y\^0//g;


# And print it out
print "The result is: \n(x + y)^$power = $result\n";