@ip = qw\10.0.0.1 10.1.2.3 192.168.12.5 77.75.0.1\;
@subnets = qw\10.0.0.0/24 10.1.0.0/16 192.168.0.0/12\;

foreach $ip (@ip){
	@a = split /\./, $ip;
	$di = getIp(@a);
	foreach $subnet (@subnets){
		($a, $b) = getNetwork($subnet);
		if(($di >= $a) && ($di <= $b)){print "$ip in $subnet\n";}
	}
}

sub getIp {
	return ($_[0]*256*256*256) + ($_[1]*256*256) + ($_[2]*256) + $_[3];
}

sub getNetwork {
	@a = split(/[\/|\.]/, +shift);
	return (getIp(@a[0 .. 3]), (getIp(@a[0 .. 3]) + (2 ** (32 - $a[4]))));
}