There is a company called MediTech in Massachusetts that uses a derivative language of MUMPS called Magic. I know several programmers that have worked there. There are thousands of engineers writing in this language as we speak.

From what I can remember:

-Only global variables

-Variables must only be capital letters, maximum length 6. If you run out of variables, you must cleverly use them in a routine and set them back to what they are. This means you can't use a name like myVar - you use AAAFD, ZBVCXZ, etc.

-System functions are usually things like ., >, ', ], so code looks like .'AAAF]{\;:..

-Meditech writes all of their own languages, databases, operating systems, tools, etc. You can only write in a non-Meditech language if you get approval from a multi-tiered architectural design board, which barely ever happens

-The founder hated C with undying passion. No one is ever allowed to use C

-All programming hires go through a 6 to 12 month training process to learn the tools, languages, and systems. As they almost exclusively hire non-CS majors, such as math and physics majors, they don't typically have a programming background and don't realize how bizarre the MediTech stack is

Because MediTech engineers get experience in a proprietary suite of technologies that is only used there, it is extremely difficult for them to get new jobs at the same pay grade and experience level. 5 years at MediTech is worth 0 years anywhere else. However, I have hired a few of these people, and while they knew nothing about say Python, JS, Linux, etc. when hired, their deep understanding of how computers work made them very skilled once they picked up the modern technologies. Not many engineers program for years in low-level nightmare languages before touching JavaScript or Python, most start high-level and go lower. The foundation provided by working in a language like Magic makes them know computers at a deeper level than most.