Better yet, a central place to WORK on *any* CPAN module. Imagine the wiki idea, but with code + comments rather than just comments. Imagine that you could click your way through the code for say, Date::Manip, cheerfully categorising algorithms (finite state machine here), doing tiny cleanups on code (doesn't handle corner case X), suggesting and branching new areas to work on larger refactorings, add tests to the test suite, and have that all linked into a system that automatically builds stable and beta branches, runs the test suites, and indicates their status, and permits CVS/Subversion checkouts of any given tree by ID or a gzip'd download of same for the purposes of testing on your local system.

Imagine running into a bug in a CPAN module and not having to file a bug report, simply hopping onto the site and branching in a fix with a comment, and adding a test case.

Imagine running a class for programming students, and being able to assign homework as walking through certain CPAN modules categorising algorithms or patterns.

Imagine having 20 minutes without anything to do, hopping onto the site and refactoring a tiny mess in a single function in a random module into something clean and elegant.

Imagine a site where sections of code have been voted especially clean, or especially messy and deserving of attention, so that rather than avoid using them or reimplementing from scratch, they can be bit-by-bit cleaned up and refactored.

Imagine a site where common code across many modules is regularly identified and abstracted into a common module, slowly building up a pool of best-of-breed module support code created and reviewed by many, used in many modules. No more hackish reimplementations, just a slowly expanding core of solid code.

Imagine contributing a module and watching it grow and stabilise every day as people from across the world spend a little bit of their time commenting and cleaning and refactoring.

Wouldn't it be cool? :)