hxtoc(1) on Linux
The text 1a271d5af888, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch) shipped it.
insert a table of contents in an HTML file
Flags it lists
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-d -
-f -
-t -
-x