Tool Command Language. It's a shitty stringly-typed scripting language from the 80s that took a neat hack (function bodies are string literals) way too far.

It's a bit less shit than Bash, but shitter than Perl.

Unfortunately the entire EDA industry has decided to use it as their scripting interface, which isn't too bad in itself - the commands they provide are pretty simple - but unfortunately it leads to people stupidly basing their entire EDA infrastructure on TCL rather than wrapping it in a saner language.