use strict;
use warnings;

my @ips = qw(123.156.89.12 12.245.67.1 12.45.67.180 12.145.66.20);

@ips = map {sprintf "%d.%d.%d.%d", split /\./} sort
    map {sprintf "%03d.%03d.%03d.%03d", split /\./} @ips;

print join "\n", @ips;

##</code><code>##

12.45.67.180
12.145.66.20
12.245.67.1
123.156.89.12