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

package main;


my $suspect = '72.31.79.5';
my $suspect2 = '255.255.255.0';


&is_hostaddress($suspect, $suspect2);

sub dec2bin {
    my $str = unpack("B32", pack("N", shift));
    return $str;
}

sub bin2dec {
    return unpack("N", pack("B32", substr("0" x 32 . shift, -32)));
}

sub is_hostaddress {
        
	my $ipaddr = shift;
        my $netmask = shift;

        return unless defined($ipaddr) && defined($netmask);

        my $binipaddr = unpack('B32', pack('C4C4C4C4', split(/\./, $ipaddr)));
        my $binnetmask = unpack('B32', pack('C4C4C4C4', split(/\./, $netmask)));
        print "ip addr = $binipaddr\n";
        print "netmask = $binnetmask\n";
#
#  Convert the mask back to a decimal integer before
#  attempting to negate. Negating directly gives 
#  Interesting results.
#
        my $ugly = ~ $binnetmask;
        my $not = dec2bin( ~ bin2dec($binnetmask));
        print "badmask = $ugly\n";
        print "notmask = $not\n";
        my $result = $binipaddr & $binnetmask;
        my $result2 = $binipaddr | $not;

        print $result;
        print "\n";
        print $result2;
        print "\n";
}