Obfuscating the key using perlcc is not the answer. The only setup I have seen that seems remotely comforting is a multi-tier design where the box that has the keys is running no services, and can only be passed transactions. (i.e, it can't be queried).

Something like:

Internet =====> Firewall ===> 
        DMZ Web Server ==> Firewall ==> 
               Seriously Locked Down CC Processer 

The 'CC Processer' box should be running no services at all, and listening on only one socket. This socket should accept inbound transactions and return an ack/nack, and nothing else. This would mean that administration, key changes, logging in, etc, would have to be done at the console. The web server should only have CC number while they are in transit, and should never write them to disk.

The folks at VISA have a pretty decent summary of what should be done to protect machines with CC data. ( It's a bit lacking on implementation details, but still good.) See: The VISA CISP Tech Info page.