Check out www.amazon.com they do (at the front end) what I personally think is a good method of handling cc transactions.

If you can't get enough info from their website, you may wish to read Amazon's patent to get a better idea of how their system works. After that of course don't plan on doing anything like it, unless you want to pay them a whole lot of money.

Then read Why Boycott Amazon?

Oh, and just so this is still Perl-related, I highly recommend Crypt::RSA as well.