Update: My guess is that you would like to change the mouse pointer to an hourglass shape to show that your program is busy while it's running, and then swap back once complete. Such a thing is fairly easy within Tk apps by calling $mw->Busy/Unbusy. As others have pointed out, there are other ways of showing that a program is busy... but if the goal is to change the cursor used by the pointer, then you are going to need either X or a library layered atop X for Unix.

You might take a look at X11::Protocol. I think that it might be possible to do what you'd like with that, but it's not going to be easy if you haven't done much with X.

Rob