#!/usr/bin/perl
# Copyright 2004-2013, Paul Johnson (paul@pjcj.net)
# This software is free. It is licensed under the same terms as Perl itself.
# The latest version of this software should be available from my homepage:
# http://www.pjcj.net
use strict;
use warnings;
sub my_sqrt
{
my $n = shift;
if ( !defined($n) || ($n < 0) ) {
return undef;
}
return sqrt($n);
}
my_sqrt(25);
my_sqrt(-2);
my_sqrt(undef);