scratch.clj

(let [#^java.util.regex.Pattern valid-chars
      #"(?i)^[a-z0-9!$&*-_=+<>/.?%][a-z0-9!$&*-_=+<>/.?]*$"]
  (defn clj-id? [#^String s]
    (if (and (not (zero? (.length s)))
             (.. valid-chars (matcher s) matches)
             ; (== (int -1) (.indexOf s ".."))
             (let [slash (.indexOf s (int \/))]
               (or (== (int -1) slash)
                   (== (int -1) (.indexOf s (int \/) (inc slash))))))
      true
      false)))