"an Access database as a back end" .. "we make money selling risk management services" .. "our take on this is quite novel". Heh. Sorry, had to!

Presumably you just are wanting to obfuscate your perl in some way. Maybe Extutils::Embed or perlembed will help. Looks like line noise to me! (Caveat.. I never touch the stuff). You could also put it in an encrypted filesystem and decode it to ram but it all seems very iffy (experimental maybe not so secure) and maybe not legal.

You can certainly decrypt things to evaluate into a standard perl program, but where do you put the key? Maybe if you hid half of it on your own server, and convinced them it has to contact you to run (once each time the mod_perl restarts).

Maybe now is a good time to start a web app. service provider, or perhaps just a little SOAP::Lite? That way they think they're getting the code but the part that does the job (the code not just a key) stays safe with you at home.