One thing I've found that it is extremely important to be able to recreate exactly the same environment. This is useful for deployment, debugging, etc. We've run into too many problems where we see a problem in production that we can't reproduce in development. That's why want to store perl and the modules in the repo. We also have a global perl install, and it's causing too many problems. For one thing, you can't add/modify a module without potentially disrupting someone else's work, and then keeping dev, test and prod in sync is a pain.

Re: prove... that would be helpful if we had any unit tests. :-)