Since TIMTOWTDI, you can also do this (slightly tested code)..

#!/usr/bin/perl
use strict;
use warnings;
use NetAddr::IP;

                # Beware large IP sets...
print join("\n", map { $_->addr } sort map { new NetAddr::IP $_ } <DAT
+A>), "\n";
 
 
__DATA__
10.1.5.2 
10.1.1.2
10.1.0.1
10.1.1.0
10.1.1.1
10.1.5.1
[download]

Best regards

-lem, but some call me fokat