The real question is do you want to collect output from the processing in the thread? You don't say what the rest of the Tk gui is doing, like tailing a log file, or receiving and printing results? Is the command you are running in the thread, run thru system or backticks? See PerlTk on a thread... for tips on setting up a Tk thread. If you want to delay the start of the processing, until a button is pressed, try making a sleeping thread, which wakes up on a button press, as in Tk-with-worker-threads. The thing to notice with a sleeping thread, is you create it before any Tk is called, you put it in a sleep loop, waiting for a shared variable to change, which signals it to wake up and start processing.