Sorry, should have been more clear on this: you'll need at least one Perl to bootstrap the others with, that's usually the system Perl, so reinstall that using your system's package manager. The advantage of the methods I described is that they don't touch the system Perl.

Things get worse. I supposedly installed perl using "dnf install perl" in Fedora 31, which seemed to work OK. However, I now have no command "perl" in any of my "bin"s and no paths in @INC. I looked for a simple perl tarball, like I used many years ago, but can't find one, only "ActivePerl-5.28.1.0000-x86_64-linux-glibc-2.12-f7fd6fde.tar.gz".

That's strange. Unfortunately I don't know enough about Fedora to give any concrete advice here; it does look like that's the correct package. Have you tried uninstalling the package first, and/or forcing its installation?

You can get the Perl source at https://www.perl.org/get.html#unix_like, as well as precompiled binaries, although in my experience those are rarely needed on *NIX. You can theoretically build a system Perl from scratch, but I'm pretty sure using Fedora's packages will be better in the long run.