You say that you're trying to use Win32::GUI and threads. It sounds like something isn't behaving the way that you were anticipating, but you're not providing information on what it is that you believe is a problem. This is like asking a mechanic what's wrong with your car without providing details about the problem or asking a doctor to give you a medical diagnosis without giving any information on the medical issues that you are having. If you want to get some help, then I would suggest that you help yourself by providing more details on what you are having issues with.

Are you sure that the code you posted is the code that you were testing? The line with sub Window_Terminate{-1} is missing a semicolon at the end, which could potentially prevent your code from running.

I personally have used Win32::GUI and threads so I can definitely say that it is possible to use the combination. As I have already mentioned, since you're not providing information about what problem(s) you are having, it's going to be nearly impossible for others to be able to help.