This is a GUI Toolkit. Tcl is itself a scripting language somewhat like Perl. The Perl community found a way to bring this Tk into Perl. I also like doing graphics in the Tk Canvas widget. I especially like the fact that Tk manages all of the details of keeping track of objects drawn onto the Canvas so that any drawn object like a line, bitmap, rectangle or Text can be selected with the mouse.
Callbacks are also easy to install.
I've been having a little bit of minor problems with Gnome. Every once in a while when I login, the Gnome session startup is very, very slow. This makes everything involved with login very slow so that it could take a couple minutes to login. Since the logout activitiy also has to connect to the gnome session, it was also not working. Thus I'd have to init 6 as root.