within each set. For example in texinfo mode:
(setq outline-heading-alist
- '((\"@chapter\" . 2) (\"@section\" . 3) (\"@subsection\" . 4)
+ \\='((\"@chapter\" . 2) (\"@section\" . 3) (\"@subsection\" . 4)
(\"@subsubsection\" . 5)
(\"@unnumbered\" . 2) (\"@unnumberedsec\" . 3)
(\"@unnumberedsubsec\" . 4) (\"@unnumberedsubsubsec\" . 5)