Here's a nice debugging feature in Clojure. The inspect module lets you look at variables in a popup JFrame. The two examples below show how you quickly view data in a table or tree format. This is really handy to quickly view data from the REPL.
(clojure.inspector/inspect-tree '(1 (a b) 2 (c d) 3 (e f )))
2016-10-24 Emacs News
8 hours ago