texinfo-update-menu-lower-regexps

texinfo-update-menu-lower-regexps is a variable defined in `texnfo-upd.el'.
Its value is

((1 concat "\\(^@\\(" texinfo-chapter-level-regexp "\\|" texinfo-section-level-regexp "\\|" texinfo-subsection-level-regexp "\\|" texinfo-subsubsection-level-regexp "\\)\\>[ 	]*\\)")
 (2 concat "\\(^@\\(" texinfo-section-level-regexp "\\|" texinfo-subsection-level-regexp "\\|" texinfo-subsubsection-level-regexp "\\)\\>[ 	]*\\)")
 (3 concat "\\(^@\\(" texinfo-subsection-level-regexp "\\|" texinfo-subsubsection-level-regexp "\\)\\>[ 	]+\\)")
 (4 concat "\\(^@\\(" texinfo-subsubsection-level-regexp "\\)\\>[ 	]+\\)")
 (5 . "a\\(^\\)"))

Documentation:
Regexps for searching for lower level sections in a Texinfo file.
The keys are strings specifying the general hierarchical level in the
document; the values are regular expressions.