Well, there is at least one POE component on CPAN for driving mpg123.

Waxing editorial . . .

Then again, there's the overriding "If it's not broke . . ." sentement. Playing MP3's requires quite a bit of number crunching (which isn't perl's fort&eaccute;), and Tk just looks so circa-early-90s-Motif-esquely ugly. XMMS and WinAmp:

• Already exist
• Already work

Unless you're interested in signal processing or something to use Inline::C with, you could probably find a better project.