Oh yeah, you have a windows version that dosn't like tk's fileevent method. Some windows versions can use it, others can't. In that case, instead of a fileevent, you can setup a timer
to do the read. You would need the timer to be faster than the log-line-writing speed, so you don't miss a line.
But you are probably better off using the win32 modules that jdtoronto showed you. See Perl/Tk App and Interprocess Communication for a discussion. BrowserUk shows some nice threaded methods that work on win32.
Also use the Search Box and search for "win32 tail" for some other ideas.