This looks interesting, but the examples don't really show off Marcel's power. The example you just gave without Marcel is:

  find . -type f -mtime -3

The example on this page: https://www.marceltheshell.org/list-processes

  ps -u djt | map (p: p.signal(9))

That's:

  pkill -9 -u djt

The example for summing files by extension is a bit more interesting:

  ls -fr | map (f: (f.suffix, 1)) | red. + | sort

Vs something like:

  find . -type f | awk -F. '(NF>1){print "."$NF}; (NF==1){print ""}' | sort | uniq -c

That said, every time I look into one of these shells, I end up sticking with bash. When it gets to the point that I need something more powerful than bash and the Unix command line environment, I'd just as soon write a stand-alone program which I can check into version control, use on remote systems that don't have one of these fancy shells installed, add proper tests, etc.

This is a neat project though. I'll keep an eye on it.