Also, I know that I am using Perl version 5.8.3 on WinXp, but how can I find out which version of TK I am using?

Assuming that you are using a Build of Perl by ActiveState for Win32, simply type the following in on a command prompt to get the version of Tk that you are using:

ppm query Tk
[download]

What is the significance of $|++? I was advised by a Monk here long ago to use it, However not sure exactly what it does?

In a nutshell, $| is a special variable that controls Perl's output buffer flushing; for a good explanation of the significance of $|++, please read the wise and insightful replies to the following node:
What the heck does $|++; do?