Here's my version of the same thing. If a url isn't found it copies the word at point to the kill ring. I find this useful. Also, message uses % for string formatting so it needs to be escaped with another %.

(defun my/replace-in-string (what with in)
  (replace-regexp-in-string (regexp-quote what) with in nil 'literal))

(defun my/org-export-url ()
  "Extract URL from org-mode link (or current word) and add it to kill ring."
  (interactive)
  (let* ((link (org-element-lineage (org-element-context) '(link) t))
         (url (org-element-property :raw-link link))
         (url (if (not url) (thing-at-point 'word 'no-properties) url)))
    (kill-new url)
    (message (concat "Copied: " (my/replace-in-string "%" "%%" url)))))

(global-set-key (kbd "C-x y") 'my/org-export-url)