FWIW, my first lisp was one called PLT Scheme. Most people know it as Racket nowadays. There's been a couple decades' worth of divergent evolution since then,

FWIW, my first lisp was one called PLT Scheme. Most people know it as Racket nowadays. There's been a couple decades' worth of divergent evolution since then, so that it's not actually compatible with any Scheme standard anymore. At least not by default -- there's still "#lang r5rs". In any case, one could be forgiven for thinking Racket is still just another flavor of Scheme.