I have five different Perls on my windows box (I like strawberry so I have 4 versions of that and one Active State for running PerlApp) for testing and application distribution. I use .bat files to manage the various settings that need to be adjusted and this works very well for me. Like IG I also have a large number of modules I "play" with over time. What I do is use my programming IDE to scan all of my active perl code and make a list of my "use" statements and then I know what modules I "need" to test first when moving to a new version of perl. I support five active products and this process takes me about 30 minutes to.