Most Lisp modes for Emacs have an eval-sexpr-at-point command which allows you to send the current sexpr to the REPL. This is in SLIME for CL but even the most basic Scheme mode has it as well.
Clojure's Emacs REPL also has this; it's strange that the article does not mention it, but talks about copying back and forth between REPL and suorce, which I consider a antipattern and really ugly workflow.
Emacs can do this with Ruby, Python... Hell, you can get it to eval buffer, region, line with anything that'll accept input and return a useful output.
The ease at which one can get any language (or I/O machine) to play along with this workflow in Emacs is astonishing.