Interestingly the "%else" would actually be cataphoric, as you refer to what comes next rather than before. So "co-referential macros" would be more fitting if you want to stick with the linguistics analogy. But that'd be too exotic of a term.

And yes as akkartik notes, it causes multiple evaluations right now, mostly just laziness and indecision on my part. I'll probably be giving control over this. Here's a real example of code where you actually want current behavior:

  (aif (ns-resolve *ns* 'specs)
    (let [c (compile spec :name name)]
      (swap! (var-get %test) update (:property c) set/union #{c}))
    (do (intern *ns* 'specs (atom {}))
         %then))

You could still have repeated use within a '%then' or '%else' block:

    (aif (test)
      (something)
      (do %then %then))