You have a basic design flaw, and you probably should consider a different approach. Even if the process is ouside the AddItem sub, you will have to somehow detect that the thing has ended and set a flag, or something.

I'm not using Windows, and the Win32::ProcessCreate idea is what you are after. Also IPC::Run is supposed to work on windows, which would allow you to run the process thru IPC, then monitor it's STDOUT, and wait to detect something which signals the "end condition". Then you can set a flag.

Perhaps the simplest way is to forget about spawning another process and just include the code from the command -line version I have into the Tk version -- Ugh. More maintenance dramas...

You can also run the process through threads, and use threads:shared to signal back to the main thread that the thread has finished running the code.