I first encountered TCL embedded deep within an electronics CAD package, and without any experience in TCL, managed to figure out how to write a small proc to simply design testing by running a signal pattern test at varyied periods and levels. It was about a year before I would take a second look at the language, and have found it quite to my liking since.
Unlike Perl, TCL is actually quite readable, and still retains an impressive degree of flexability, letting me do what I need to do. I like it. :)
Topics of particular interest to me so far: