Actually, Racket and Clojure share very little in terms of syntax and semantics. Lisps are like that: they all have parens and frequently that's the end of similarities. Semantics of Common Lisp, Emacs Lisp, Scheme, newLISP - not to mention Shen - are very different. You should treat them as separate languages, especially when learning. So, in short (I went Racket->Clojure), there are no problems if you remember not to write Racket in Clojure and vice versa :)