Emacs word toggles

word-toggle.el

;;;###autoload
(defun capitalize-word-toggle ()
  (interactive)
  (let ((start (car
                (save-excursion
                  (backward-word)
                  (bounds-of-thing-at-point 'symbol)))))
    (if start
        (save-excursion
          (goto-char start)
          (funcall
           (if (char-upcasep (char-after))
               'downcase-region
             'upcase-region)
           start (1+ start)))
      (capitalize-word -1))))

;;;###autoload
(defun upcase-word-toggle ()
  (interactive)
  (let ((bounds (bounds-of-thing-at-point 'symbol))
        beg end
        regionp)
    (if (eq this-command last-command)
        (setq regionp (get this-command 'regionp))
      (put this-command 'regionp nil))
    (cond
      ((or (region-active-p) regionp)
       (setq beg (region-beginning)
             end (region-end))
       (put this-command 'regionp t))
      (bounds
       (setq beg (car bounds)
             end (cdr bounds)))
      (t
       (setq beg (point)
             end (1+ beg))))
    (save-excursion
      (goto-char (1- beg))
      (and (re-search-forward "[A-Za-z]" end t)
           (funcall (if (char-upcasep (char-before))
                        'downcase-region
                      'upcase-region)
                    beg end)))))

(defun char-upcasep (letter)
  (eq letter (upcase letter)))