save-excursion: wrong number of arguments

the-error.txt

save-excursion: Wrong number of arguments: (1 . 1), 0
                                           ^ the number of arguments is... A DOTTED PAIR!?
                                             am I reading this right!? O_o

uhm.el

(defun dotspacemacs//haskell-toggle-qualified ()
  "toggle the qualified-ness of a single import in haskell"
  ;; TODO: sensible behavior when multiple lines are marked
  (interactive)
  (save-excursion
    (move-beginning-of-line)
    (let ((from-qual   "^import[:space:]+qualified[:space]+")
          (from-unqual "^import[:space:]+")
          (to-qual     "import qualified ")
          (to-unqual   "import           "))
      ;; (if it isn't an import line, don't do anything at all)
      (if (looking-at-p "import")
          (if (looking-at-p from-qual)
              (evil-ex-substitute "." "." from-qual to-unqual)
            (evil-ex-substitute "." "." from-unqual to-qual))))))