Unable to generate custom toc

[hounddog]

My real problem isn't really related to this file, but this works as a test case.

I want to know how can I specify the TOC using the levelX-toc options.

I tried a million things but nothing work. Here is an example.
In this case there is no match for the expression so the TOC created by calibre should be empty.
However it still shows a TOC.
How does the levelX-toc options work?

book="pg5200.epub"
ebook-convert "${book}" "${book%.*}.pdf"     --level1-toc '//*[re:test(., "\s*((foobar)\s+)", "i"]' --no-chapters-in-toc

I'm using an update version of Calibre in Linux via command line.


After I know how to do this I'll be able to fix my real problem I think.
Which would be to have all h1 tags to level2-toc and only a selected to level1-toc.


Thanks in advance for any help.


edit: added file (it was downloaded from the "EPUB (no images)" from https://www.gutenberg.org/ebooks/5200 )