Variable: comment-start-line-regexp
comment-start-line-regexp is a variable defined in newcomment.el.gz.
Value
nil
Documentation
Regexp matching the start of a line comment.
Unlike comment-start-skip, which matches the start of any comment,
this regexp matches only the start of line comments (as opposed to block
comments), so it can be used to distinguish between the two.
Modes that support both line and block comments should set this variable.
Probably introduced at or before Emacs version 32.1.
Source Code
;; Defined in /usr/src/emacs/lisp/newcomment.el.gz
;;;###autoload
(defvar comment-start-line-regexp nil
"Regexp matching the start of a line comment.
Unlike `comment-start-skip', which matches the start of any comment,
this regexp matches only the start of line comments (as opposed to block
comments), so it can be used to distinguish between the two.
Modes that support both line and block comments should set this
variable.")