Hi I'm pretty new to perlbrew, so I might be doing something wrong, but here is how I use it.

I install a version of Perl with perlbrew install, use that version with perlbrew use, then for each project / application I am going to use it with, I create a separate library with perlbrew lib create. If you perlbrew list, then you will see both perl-version and perl-version@project in the list. To use the library use perlbrew use perl-version@project. Now anything you cpan / install, will go into this library rather than the base perlbrew version, keeping things separate.

The one gotcha I found is that I now need to do perlbrew use perlversion, then perlbrew use perl-version@project, to use both the perlbrew version and library combination, but that is not a big issue

Again, I am new to perlbrew, so there may well be a better way than this