|Don't ask to ask, just ask|
Thank you thanos1983 for sharing the link. The solution there worked for me as well.
patchperl was missing from ~/perl5/perlbrew/bin/
So I did:curl https://raw.githubusercontent.com/gugod/patchperl-packing/master/patchperl > ~/perl5/perlbrew/bin/patchperl
And then[~]$ perlbrew install perl-5.28.1
This time it worked and installed perl-5.28.1.
Somehow `perlbrew available` still doesn't work but that's not a big deal for me. I'll know the version number that is available and if I want to install it or not.
In reply to Re^3: perlbrew/curl: curl: (60) Peer certificate cannot be authenticated with known CA certificates