Windows marks an application as "not responding" when it hasn't re-entered the message loop within some (fairly short) period of time. That doesn't mean the application has "hung", just that the OS hasn't noticed it do anything interesting in a while. In principle there is no way to determine if an application has "hung" - that is a problem related to the Halting_problem.

You can use Win32::Process to manipulate Windows processes, but you need the PID for a running process before you can work with it. Obtaining the PID is a bit tricky unless you created the process in the first place. I don't see any way of obtaining a "not responding" status for a process from the Win32 API (although that doesn't mean there isn't a way).