user> (use 'clojure.contrib.trace)
nil
user> (defn foo [coll] (reduce + coll))
#'user/foo
user> (defn bar [coll] (map inc coll))
#'user/bar
user> (dotrace [foo bar] (foo (bar [1 1 1])))
TRACE t7043: (bar [1 1 1])
TRACE t7043: => (2 2 2)
TRACE t7044: (foo (2 2 2))
TRACE t7044: => 6

http://groups.google.com/group/clojure/browse_thread/thread/ee9abad24909386e

Using contrib's trace ns in order to debug functions in the REPL

Clojure REPL Tracing

function

Clojure