老生常谈的一个问题，你对字面量做了破坏性操作，结果就被持久化了
(defun toc-glue-toc-to-simple-outline (s &optional lexer)
"Convert given ToC string S to simple outline format.
LEXER may be given to replace the lexer function, which accepts one line
string, return a list (level title page) of type (number string number).
If analyze failed, return NIL."
(let ((lexer (or lexer #'toc-glue--default-lexer))
(lines (split-string s "\n" t))
- (stack '((-1 bookmarks))))
+ (stack (list (list -1 'bookmarks))))