(defvar hidden-braced-blocks-overlays nil
  "Variable to store the regions we put an overlay on.")

(defun hide-braced-blocks ()
  (interactive)
  (save-excursion
    (let ((overlay-start nil)
      (overlay-end nil))
      (while
      (progn
        (setq overlay-start (search-forward "{{{" nil t))
        (setq overlay-end (search-forward "}}}" nil t))
        overlay-start)
    (let ((new-overlay (make-overlay overlay-start overlay-end)))
      (push new-overlay hidden-braced-blocks-overlays)
      (overlay-put new-overlay 'invisible t)
      (overlay-put new-overlay 'intangible t))))))

(defun show-braced-blocks ()
  (interactive)
  (while
      hidden-braced-blocks-overlays
    (let ((overlay (cdr hidden-braced-blocks-overlays)))
      (delete-overlay (car hidden-braced-blocks-overlays))
      (setq hidden-braced-blocks-overlays
        (cdr hidden-braced-blocks-overlays)))))