Read another with M-RET

[Nordlöw]

How do I modify read-string-list so that RET ends loop a single read
and M-RET finishes current input and ask for another instead of the
logic given in the code below where RET finishes current and ask for
another and a final empty string (just RET) instead ends the loop?

Thanks in advance,
Nordlöw

Here's the code:

(defun read-string-list (&optional prompt uniquify)
  "Construct a list of strings interactively from minibuffer.
An empty string (RET) terminates the read loop."
  (interactive)
  (let ((sl nil))
    (let (str)
      (while (not (equal
                   (setq str (read-string
                              (concat (or prompt
                                          "String")
                                      " (or RET to end list): ")))
                   ""))
        (if uniquify
            (add-to-list 'sl str t)
          (setq sl (append sl `(,str))))
        ))
    sl))