[hardwaresofton]

Usually, the tools themselves aren't built in TCL (they're usually C/C++), but the interface is in TCL (and some other proprietary languages, depending on which tool you're using)...

And yes, unfortunately the tools end up being old and crufty, and that was my impression of TCL.

I did a bunch of TCL while working at one of the aforementioned companies, and I got to use it enough to see the lisp-y awesome parts (if you squint hard, [ ]s are just oddly shaped parenthesis), and the smalltalk-y stuff, but I still would have preferred using a different scripting language as my interface.