Clojure has *1, *2, & *3. Common Lisp & Racket (w/ xrepl) have similar. IIRC, IPython & irb keep a list of all outputs in the current session. With readline it is certainly possible to retrieve the previous expression & wrap it with code to save the result to a variable, but something like *1 is much simpler when experimenting in the REPL.

My apologies if Fennel's REPL already has something like this. I couldn't find it. :)