#!/usr/bin/perl -w

use strict;

my @ten_factors = (['zilch', 'one', 'two', 'three', 'four', 'five', 'six', 
		    'seven', 'eight', 'nine'],
		   ['ten', 'eleven', 'twelve', 'thirteen', 'fourteen', 
		    'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen',
		    'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 
		    'eighty', 'ninety'],
		   'thousand',
		   'million',
		   'billion',
		   'trillion',
		   'quadrillion',
		   'quintillion',
		   'sextillion',
		   'septillion',
		   'octillion');

sub num2word
{
    my $num = shift;;
    chomp($num);
    
    die "NaN\," if($num !~ /^[0-9]*$/);

    $num = '0' . $num while(length($num) % 3);
    
    my $factor = 0;
    my $output = '';
    
    while($num)
    {
	my @trip = reverse (chop($num), chop($num), chop($num));
	my $trip = trip_convert(\@trip);
	if($factor > 0)
	{
	    $trip .= ' ' . $ten_factors[$factor+1];
	}
	$output = $trip . ' ' . $output;
	$factor++;
    }
    $output =~ s/zilch [a-z]*//g;
    return $output;
}

sub trip_convert
{
    my $trip = shift;

    my $retval = '';
    if($$trip[1] == 1)
    {
	$retval = $ten_factors[1][$$trip[2]];
    }
    else
    {
	$retval = $ten_factors[0][$$trip[2]];
	$retval = $ten_factors[1][$$trip[1]+8] . ' ' . $retval unless($$trip[1] == 0);
    }
    $retval = $ten_factors[0][$$trip[0]] . ' hundred ' . $retval;
    return $retval;
}