Test whether a list contains a specific value in Clojure

Question

What is the best way to test whether a list contains a given value in Clojure?

In particular, the behaviour of contains? is currently confusing me:

Answer 1

(defn which?
 "Checks if any of elements is included in coll and says which one
  was found as first. Coll can be map, list, vector and set"
 [ coll & rest ]
 (let [ncoll (if (map? coll) (keys coll) coll)]
    (reduce
     #(or %1  (first (filter (fn[a] (= a %2))
                           ncoll))) nil rest )))

example usage (which? [ 1 2 3 ] 3) or (which? #{ 1 2 3} 4 5 3)