🐧 State of the art in usage of environment variables for shell programming

Hello all! Despite my several year usage of Linux and passion for programming, I've not yet delved into the depths of several aspects of Linux itself. I'm working on that now.

As I come across environment variables, it strikes me that there's so much potential! And it strikes me as interesting that they're not typed whatsoever (useful for quick/dirty scripts, for sure).

I've not had much success in searching (although I found GNU's Guile, which looks interesting; maybe not entirely related) but I'm interested to know:

What is the state of the art in using environment variables for more sophisticated scripts/programming? It seems, for example, that we could create an entire DSL (Domain Specific Language) within such variables that could be changed at runtime -- it seems that having these variables typed would be of interest, it seems that error-checking would be desirable (e.g., if we set an environment variable in a way that depends on an external network call, we want to know if it failed or not) -- again, it seems that there'd be so much potential!

I'm certain I'm not the first to think of this, so I'm wondering what experience in these matters exist. Thanks!