Maybe I can help on this at the hackathon, but the installation document is a little unclear which method is the best (CPAN, homebrew or git).
I think many people are already using perlbrew and consider switching to plenv. In that case, installing plenv with cpanm under homebrew is quite dangerous and could lead to a confusing situation. I actually have done that initially (i.e. cpanm App::plenv under homebrew perl), and when I tried to stop using perlbrew, then there's no plenv to use anymore.
I think there's a big caveat under the CPAN section that you have to use the system perl to install plenv, like actually using /usr/bin/perl
curl -L cpanmin.us | /usr/bin/perl - --sudo App::plenv
since otherwise there's a chicken-egg problem (I think?).
Also: There should probably be an entry for "why is plenv rehash necessary after cpanm installation" in the FAQ.
The documentation was fixed by taking documents from rbenv.