Since Java programs and libraries can be delivered in a precompiled essentially unreviewable form there needs to be a way to control what they do on your system from the outside.

Nothing is unviewable (JODE). Java programmers just think that their code cannot be decompiled and modified. This leads to the culture which demerphq described. Perl grants no such illusions.

Now, if you wanted to implement some sort of immutable perl class, you'd probably need to go the Module::Signature route. You still don't have totalitarian control, but at least you can disown the modified classes. Which is actually the way it's done in java ... hey, maybe there isn't MTOWTDI. ;-)