Factorial in Perl

Welcome to the Factorial in Perl page! Here, you’ll find the source code for this program as well as a description of how the program works.

Current Solution

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

# no input
usage() unless @ARGV == 1;

# accept input as argument
my ($number) = @ARGV;

# if not provided, read from standard input
if (!defined $number) {
	$number = <STDIN>;
	chomp $number;
}

if (!defined $number || $number !~ /^\d+$/ || $number < 0) {
	usage();
}

my $factorial = 1;

for (my $i = 1; $i <= $number; $i++) {
	$factorial = $factorial * $i;
}

print "$factorial\n";

sub usage {
	print "Usage: please input a non-negative integer\n";
	exit;
}

Factorial in Perl was written by:

• Bharath
• Gabriela Kandová

If you see anything you’d like to change or update, please consider contributing.

Note: The solution shown above is the current solution in the Sample Programs repository as of Oct 16 2019 15:02:04. The solution was first committed on Oct 14 2019 22:44:32. As a result, documentation below may be outdated.

How to Implement the Solution

No ‘How to Implement the Solution’ section available. Please consider contributing.

How to Run the Solution

No ‘How to Run the Solution’ section available. Please consider contributing.