After considering a number of options, I've decided to use this package to learn more about the mobi format. As part of preparation, I've imported the extracted tar files into a git repository and uploaded that to github. I did the import with a script that I wrote for that purpose which is attached here.
The repository is at
https://github.com/jps-e/mobi-perl.git
On creation of the bare repo at github, I was surprised to learn that the default primary branch is now main. I wend with the flow and renamed the branch on my local repo before pushing it to github. That seemed to work out OK. I also named the repo mobi-perl instead of mobiperl to leave that name available in case something went horribly wrong or tompe wants to make his own and I want to clone or fork it. topme hasn't posted since 2016 or logged in since 2017.
(The script took 0.8 seconds to import the 22 tar files.)