The CPAN module offers ways to automate package downloads and installs from CPAN. But I've only played with it so I'm not an expert.

This is something I also want to solve at some point. In my mind, what I want is some sort of master make file I can take to any machine and have it build or upgrade that machine to include everything I need. I'd want that to work cross-platform and I'd want it to get any prerequisite libraries and build those. The model I like best for this is the FreeBSD ports model. If you've never used that, it allows you to install a tree that represents everything you could get for your installation. You can sync up with new versions of that tree. The tree is just a skeleton. If you actually want one of the pieces, you go to its skeleton directory and type make. If other dependencies exist, it automagically gets and builds those. It's a very clean model IMO.