There is a culture in Lisp of extending the language syntactically and semantically so that it is the last language you would ever need. The modern version of this is Racket (www.racket-lang.org) which contains all the mechanisms you would ever need to evolve a language both syntactically and semantically. If you've never encountered it, it is definitely worth your time exploring it to see how deep programming language ideas can actually make magically powerful language systems.