Sorry for not explaining in any detail at all. :) I just assumed that the link would tell the story better than I could.

perlbrew is a tool that simplifies the process of installing your own personal Perl, separate from the system's Perl. You don't even need any sort of elevated privileges on the host.

In addition to being used by individuals who need their own copy of Perl, it's also frequently used by developers who need to support older Perls as well as more current ones. I've had clients who for one reason or another are stuck with an older Perl. So I'll install that version with Perlbrew on my system so that I can be sure that I'm coding to compliance with the older version of Perl. CPAN developers also like it for helping to verify that a module they've written doesn't generate any surprises under, say, Perl 5.6.0.

It has many uses for many people. In your case, its use is to have a version of Perl different from system Perl.