The points made above are good. In addition I believe tk has issues with threads because it maintains its own state seperate to that of perl, so if you have tk objects accessed by multiple perl threads it will fall to pieces. To avoid these problems, spawn multiple threads early on, and create/interface with tk from your main thread/one thread only. Pass information or actions from your gui/tk thread to your worker threads via shared variables / thread safe queues or IPC etc. One possible advantage to this is that you have a better chance of ensuring your gui doesnt freeze during blocking actions as they will be passed to your worker threads. On the downside... your apps memory usage may well be huge by adding a gui - thats been my experience. Good luck, Rossco