FYI, your code works fine on Linux. Here is the output:

Parent 962 got PID 963 from fork(962 Computer1)
        963 Computer1

+Parent 962 got PID 964 from fork(962 Computer2)
        964 Computer2

+       965 Computer3
Parent 962 got PID 965 from fork(962 Computer3)

+Parent 962 got PID 966 from fork(962 )
        966 

+wait() ed until -1 was returned.
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Another module that you might look into is IPC::Run. I know that it has at least some Win32 functionality.