This program lets you install perl like this:
perlbrew install perl-5.10.1 perlbrew install perl-5.11.5
And then you can switch between versions at any time
perlbrew switch perl-5.11.5 perlbrew switch perl-5.10.1
Ever installed perl has their own site lib.
perlbrew can probably help you if you install perl to $HOME, like me.
If you are familiar with Ruby tools, perlbrew plays similar roles like rvm, but different. It does not install different perl from different vendor, because that diversity has been merged into one and the only perl distribution - the one that you find on cpan. (Well, there are still different vendors who distribute their own perl, but I doubt it can be easily handled by perlbrew. We'll see.)
Also perl has its own mechanism to have multiple installations of different versions on the same machine. If you are already do it that way, you probably do not need this program to help you anything.
This project was just started and need more hacking power. Maybe it'll be on my TODO list for the OSDC.tw post-conference hackathon.