+(defcustom message-forward-included-headers nil
+ "If non-nil, delete non-matching headers when forwarding a message.
+Only headers that match this regexp will be included. This
+variable should be a regexp or a list of regexps."
+ :version "24.5"
+ :group 'message-forwarding
+ :type '(repeat :value-to-internal (lambda (widget value)
+ (custom-split-regexp-maybe value))
+ :match (lambda (widget value)
+ (or (stringp value)
+ (widget-editable-list-match widget value)))
+ regexp))
+