camelcasefy.el

(defun camelcasefy ()
  "Convert a string in camel-case interactively."
  (interactive)
  (catch 'exit
    (let ((stack nil))
      (while t
        (let ((ch (read-char "Character: ")))
          (cond
           ((char-equal ch ?\n)
            (throw 'exit nil))
           ((char-equal ch ?\d)
            (downcase-region (point) (1+ (point)))
            (let ((point (pop stack)))
              (when point
                (goto-char point))))
           ((char-equal ch ?\s)
            (downcase-region (point) (1+ (point)))
            (forward-char)
            (pop stack))
           ((char-equal ch ?\t)
            ;; Undo the current one
            (downcase-region (point) (1+ (point)))
            (pop stack)
            ;; Capitalize the next instance of the character
            (push (point) stack)
            (let ((ch (buffer-substring-no-properties (point) (1+ (point)))))
              (search-forward ch))
            (upcase-region (point) (1+ (point))))
           (t
            (push (point) stack)
            (forward-char)
            (search-forward (string ch))
            (backward-char)
            (upcase-region (point) (1+ (point))))))))))