Fun fact: macOS hex editor "Hex Fiend" uses Tcl for its templating language:

https://github.com/HexFiend/HexFiend/tree/master/templates

The industry standard VFX compositing tool Nuke also uses Tcl for its expressions and save format, it's all Tcl terms as I recall. My brother did VFX for a while and I was amused when he was having some trouble with an expression and I was like "it's a Tcl system... I know this" and helped him.