I don't use threads so I can't really answer your question, however I have seen a few reports saying that Moose and threads do not always work well together. Currently none of the Moose core developers actually use threads and all generally believe them to be broken by design anyway. That said, we would still appreciate a bug report and failing test case if you can isolate one.

You might want to look into something like POE or AnyEvent as an alternative approach to mulitprogramming, both these two modules are known to work well with Moose.