If you really want to secure Perl code I would say you would have to hack the perl binary. Of course you would be in a licensing jungle in that a lot of commonly used modules are released under the GPL and not under PAL, so you'd have problems there. And if you allowed the user write access to _any_ such source then they would have an opportunity to bypass your security measures and use deparse to recreate the code. So IMO a properly secured Perl based application A) isnt going to use the normal Perl exe, and B) is probably going to be functionally crippled to the point where id be curious if it would be worth it.

IMO a lot of the more intelligent businesses are going to want source code level access anyway, so I dont really see the point. Of course there are enough stupid companies that wont that you could probably make a business out of it anyway.