I'm very glad I learned tcl, even though it wasn't particularly enjoyable for the first few weeks of it.

We built an online retail trading platform in tcl. Do not recommend that, but I sure did learn a damn lot about computing. For non-technical reasons, that business failed (parent company got devastated in the LTCM bond fiasco and sold off all their satellite units, one of which was ours).

I've used it several times since as a glue language (where it's much more fitting, IMO) and that's been productive.

>other languages, due to having more data flexiblity, allow you to use less powerful tools, like lambda functions

Tcl has had lambda functions for over fifteen years.