Hmmm...that's interesting...

Tk version 804.029

perl -v

This is perl 5, version 14, subversion 2 (v5.14.2) built for i386-linux-thread-multi

I guess I can try the code on another machine w/different versions of perl/Tk...in the mean time, can anyone else replicate it?

Edit: Seeing the same issue on CentOS 6 box with perl v5.10.1 and Tk 804.028

Edit2: And in case it is related to WMs...also seeing the issue in Fluxbox in a VNC session, in F16/Gnome 3.2.1 desktop, and RHEL6.0/Gnome 2.28 desktop.