[exim] bash or perl question

There are probably people out there who just know how to do this in a
simple way.

I have two files. Both files are text files that have IP addresses on
separate lines. Both are alphabetical. What I want to do is read file A
and file B and create file C that has all the IP addresses in file A
that do not match the addresses in file B.

Trying a new spam processing trick creating a whitelist of every IP
address where I got 10 or more hams and no spams. That way I can just
have a host whitelist that I don't have to run through spamassassin.

Thanks in advance.