So I recently mentioned the provisionally-named PerlDJ, my Perl/Tk DigitalDJ clone. What I didn't know then, and just now discovered, is that something that differs between babylon5, the machine I'm working towards reinstalling with Gentoo, and whitestar which already runs Gentoo 10.0, is causing PerlDJ to not work properly. It seems to be something in dev-lang/tk on Gentoo. Specifically, what's going wrong is that on Gentoo, PerlDJ blocks on the Tk interface MainLoop(), and will not come out of MainLoop() until something — ANYTHING — happens in PerlDJ's window. It can be as simple as a focus change or even just a mouse move, but something has to happen in the window before MainLoop() will yield.
Also, on Gentoo, PerlDJ goes into an infinite loop on exit. I'm not sure what's behind that yet. It's kind of moot unless I can solve the UI blocking problem.