branch_return_sub

#!/usr/bin/perl

# Copyright 2004-2011, Paul Johnson (pjcj@cpan.org)

# 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);