This is probably of no great help in resolving your problem, but it may help to define the parameters of the issue when you submit your bug report.

Run in debug mode your script outputs 1.3 from the first print, hangs for a few tens of seconds, then exits without generating output from the second print or entering Mainloop on Windows using Perl 5.10.1 and Tk 804.029.

Run normally the script runs as expected under Windows.