I wrote a Tetris clone called Spew using OOPerl and Tk. The source code is included along with a windows binary.
Download Spew here
The main problem I've come across with OOPerl and Tk is that you still kind of have to treat the MainWindow object as a global variable. I get around that by passing in the MainWindow object as a variable to the objects that need it.
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Washizu Acoustic Rock