This looks like the other completely normal, idiomatic Clojure programs I've seen which manipulate a StringBuilder. And as Clojurians go I'm far to the succinct

This looks like the other completely normal, idiomatic Clojure programs I've seen which manipulate a StringBuilder. And as Clojurians go I'm far to the succinctness/concision-preferring end of the spectrum. I'm curious to see your core.async-based version :)