Erlang early-returns via syntax sugar rather than throw-catch.

lfe_ablock.lfe.clj

;; ([{atom(),binary()}], pid()) -> {missing,atom()} 
;;                               | {bad_value,atom()} 
;;                               | {unescaped,|atom()} 
;;                               | malicious 
;;                               | ok.
(defn sanitize [args logger-pid]
  (ablock user-err
    ; check for user screwing up the input, inform them
    (check-missing args)
    (if (/= '() it)
      (return-from user-err (tuple 'missing it)))
    (proplists:get_value 'id args)
    (if (not-numeric? it)
      (return-from user-err (tuple 'bad_value 'id)))
    (proplists:get_value 'email args)
    (if (invalid-email? it)
      (return-from user-err (tuple 'bad_value 'email)))
    ; check for malicious-looking screwups, don't inform
    ; them and log to the user's logging process
    (ablock malicious
      (orddict:map (fun check-sql-escapes 1) args)
      (orddict:filter (cut /= 'ok <>) it)
      (if (== 'email (element 1 it))
        (return-from user-err (tuple 'unescaped 'email))
        (return-from malicious it))
      (if (size-too-big? args)
        (return-from malicious 'size_dos))
      'ok)
    (if (/= 'ok it)
        (progn (: user_logger malicious logger-pid it)
               (return-from user-err 'malicious)))
    (tuple 'ok args)))