I would try re-installing Term::ReadKey. Also, instead of looping with ReadKey(-1), you could try just calling ReadKey(0) once.

You could also check $! to see if getc returned an unexpected error. Note, however, that $! is not reset to 0 automatically, so you should clear it out beforehand, and that some errors would be expected--what error you would normally get when no character is available may differ by operating system.