Comment explaining a regex

find-from-regex

;; Some documentation of this regular expression from hell, so I have
;; some hope of debugging it later.
;;
;; Start with the core "inner" regex:
;;
;;    [\w\-]([\.\w])+[\w]+@([\w\-]+\.)+[A-Za-z]{2,4}
;;
;; This matches a "bare" email address, like bhurt@spnz.org.  Then we
;; decorate it- we want to match the email adress even if it has a
;; name attached, like: "Brian Hurt" <bhurt@spnz.org>
;;
;;   \"([^\"]|(\\.))*\"\s*<$bare$>
;;
;; where $bare$ is replaced with the bare-email matching regex above.
;; Except we want to match either a bare or decorated email address,
;; so it's really:
;;
;;   ($bare$)|(\"([^\"]|(\\.))*\"\s*<$bare$>)
;;
;; Note that $bare$ is now duplicated twice.  Now we want to match
;; a comma seperated sequence of decorated (including bare) email
;; addresses, so we do:
;;
;;     ($deco$\s*,\s*)*$deco$
;;
;; where $deco$ is the decorated or bare email address matcher above.
;; Now we want to match a line that starts with "from:" followed by
;; a comma seperated list of email addresses, and nothing else:
;;
;;     ^\s*from\s*:\s*($addrs$)\s*$
;;
;; where $addrs$ is our comma seperated list of email address matcher
;; above.  Lastly, we want to set the following flags:
;;    i = case insensitive matching
;;    d = unix new lines
;;    m = multiline matching
;;
;; so we prepend (?idm) to the regular expression.