I use Win32::GUI a lot, but I also don't know that much about the internals. I would suggest checking out this list. The search feature on sourceforge is awful but there's a lot of info there and the list members are very helpful.
Thanks. I did check that list but couldn't find anything definitive there or on google which is usually my first stop. After extensive searching, I usually ask here first just because the answers are quite often better, the format is nicer, and the atmosphere is generally friendly. I will post the question there if nothing turns up here but I hate to double post.