Of course, if you're running it in MS win32, you should be aware that any "stay on top" windows (such as the taskbar and, on my computer anyway, Trillian) will still be in front. You'll have to do something using Win32 or Win32::API to move them to the back, probably. Although, it's possible Tk has some way to force a z-order for your window (I haven't checked).

bbfu
Black flowers blossum
Fearless on my breath