I can help with the gentoo dist, though the perl I have running in it is at version 5.8.5. Sadly my gentooishness is always on the ~x86 bleeding edge of things... May want to check changelog entries... I may do so just to investigate as well. From running and downloading I recieved no endless loop. But i don't have Tk.pm so I'll try again after installing (ewwww... ) ;)
After all that and whatever else it required it runs fine, I suspect, as I'ven't read the manual yet.
The only problem that comes to mind that would cause some misbehavior like this would be the TermUI.pmperhaps in conjunction with Term::ReadKey stuff getting "wackadoo" this is a wild guess. Who knows it might narrow things down.
The reason for my suspicion is that I noticed it takes much longer than I feel comfortable with to absorb a CTRL+Z and CTRL+C from the keyboard.
This might be one of those edge cases where... Perl 5.8.4 + whatever other versions of modules the user in question posesses and perhaps even more insidious whatever other versions of C style system libraries that they wrap/depend might be leaking oil so to speak with the users particular Debian (kernel/libs/perl+TK depends) stew... HTH.