Commands
M-x
	re-builder
		pops up a separate window in which you can test out your regexp, and any matches
		in your original buffer will get highlighted as you edit your regexp.
	occur
		prompts you for a regular expression, then displays in a separate buffer a list of all
		lines in the current buffer which match that regexp (as well as their line numbers).
		Clicking on any occurrence takes you to that line in the buffer.


C-c
	C-q
		reb-quit
	C-i
		reb-change-syntax
	C-c
		reb-toggle-case
	C-b
		reb-change-target-buffer

    (define-key map "\C-c\C-w" 'reb-copy)
    (define-key map "\C-c\C-s" 'reb-next-match)
    (define-key map "\C-c\C-r" 'reb-prev-match)
    (define-key map "\C-c\C-e" 'reb-enter-subexp-mode)
    (define-key map "\C-c\C-u" 'reb-force-update)


sregex

  (sregexq (opt "resent-")
           (group (or "to" "cc" "bcc"))
           ": "
           (backref 1))  =>  "\\(resent-\\)?\\(to\\|cc\\|bcc\\): \\2"