https://screwlisp.small-web.org/cl-series/intern-everything/
Short article #clseries #lazyEvaluation #efficient #commonLisp #lisp . Just an example of using series to in-place alter a nested list by acting on its scanned fringe, incrementally in a repl.

(defparameter *list* '((a 1 b 2) (3) 4 (((c)))))
*list*
(require :series)
(series::install)
(scan-lists-of-lists-fringe ***)
(#Mformat (series nil) (series "~a") *)
(#Mintern *)
(alter *** *)
(series::install :remove t)
*list*

Oh that's actually the whole thing (- explanation)