I don't have Perl/Tk handy, but I think you need to finish up with

MainLoop;
[download]

I found the answer googling; came up with this answer in the comp.lang.perl.tk FAQ.

Edit:Also, check out Perl TK for more wisdom from the monks here about Perl/Tk.
Edit^2: Hmmm, I _do_ have Perl/Tk installed, and that does work. Thank you, ActiveState :)
--
Mike