use Socket;
sub add_to_ip($$)
{
  my( $ip, $add ) = @_;
  inet_ntoa pack( 'N', unpack('N',inet_aton $ip) + $add )
}

##</code><code>##

$j = add_to_ip( $i, 1 ); # simple increment
$j = add_to_ip( $i, -1 ); # simple decrement
$j = add_to_ip( $i, 300 ); # addition carries over into the next-to-last quad.