Ironically while Rails might have done the headlines for Ruby, almost a decade before, we were using many of the same ideas in AOLServer, Vignette, Safelayer (our own implementation back in the .com wave)

https://en.wikipedia.org/wiki/AOLserver

https://en.wikipedia.org/wiki/StoryServer

So back in the early days of Apache and server modules, Tcl was a good option to build web applications. :)

I've mainly see it used in HDL tooling to glue disparate tools together.

That being said, it grew on me as a general scripting language kind of generally in the same space as Perl.

The last paragraph answered my question:

"Tcl continues to be heavily used as an embedded scripting language, a domain where it still seems to be the best alternative"