[$] An alternate pattern-matching conditional for Elisp

One of the outcomes of the (extremely) lengthy discussion about using
Common Lisp features in Emacs Lisp (Elisp), which we looked at back in November, was an effort to
start removing some of those uses from Emacs. The rewrite of some of the
Elisp in Emacs that uses the Common Lisp library (cl-lib) was started by
Richard Stallman as a way to reduce the cognitive load needed for
maintaining Emacs itself. Since then, he has broadened his efforts to
simplify Elisp by adding a new pattern-matching
conditional that would be a competitor to pcase,
which is a longstanding macro that he finds overly complex.