What are es and rc? Can you give some links?
https://en.wikipedia.org/wiki/Rc_(Unix_shell)
https://wryun.github.io/es-shell/
They are alternative shells, both from the 90's I believe. POSIX was good in some ways, but bad in that it froze a defective shell design
It has been acknowledged as defective for >30 years
https://www.oilshell.org/blog/2019/01/18.html#slogans-to-exp...
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es shell is heavily influenced by Lisp. And actually I just wrote a comment that said my project YSH has garbage collection, but the es shell paper has a nice section on garbage collection (which is required for Lisp-y data structures)
And I took some influence from it
Trivia: one of the authors of es shell, Paul Haahr, went on to be a key engineer in the creation of Google