Suggestions about what the heck's going on will be gratefully received.

I concur with kcott and Discipulus. For your first release to CPAN don't even think about using one of the release automation tools like Minilla or Dist::Zilla, etc. They are fine for people who do a lot of releases and already fully understand the procedure but for a first-timer they will be confusing at best.

Follow the guides such as How to make a CPAN Module Distribution and just use the simple, basic tools many of which are in Core. Once you have a tarball ready for upload to CPAN, I strongly suggest that you copy it to a fresh machine and try to upack it and install your module there first. This can catch any number of problems before you upload it to CPAN.

Thanks for considering releasing your code and good luck with the release.