(defun xah-toggle-letter-case ()
  "Toggle the letter case of current word or selection.
Always cycle in this order: Init Caps, ALL CAPS, all lower.

URL `http://xahlee.info/emacs/emacs/emacs_toggle_letter_case.html'
Version: 2020-06-26 2023-11-14"
  (interactive)
  (let ( (deactivate-mark nil) xp1 xp2)
    (if (region-active-p)
        (setq xp1 (region-beginning) xp2 (region-end))
      (save-excursion
        (skip-chars-backward "[:alpha:]")
        (setq xp1 (point))
        (skip-chars-forward "[:alpha:]")
        (setq xp2 (point))))
    (when (not (eq last-command this-command))
      (put this-command 'state 0))
    (cond
     ((equal 0 (get this-command 'state))
      (upcase-initials-region xp1 xp2)
      (put this-command 'state 1))
     ((equal 1 (get this-command 'state))
      (upcase-region xp1 xp2)
      (put this-command 'state 2))
     ((equal 2 (get this-command 'state))
      (downcase-region xp1 xp2)
      (put this-command 'state 0)))))Language:Clojure