I'd suggest using local::lib, as that will take care of configuring the modules in a way that they should install cleanly to a local directory. Both cpan and cpanm can make use of local::lib; I believe the former requires a bit of configuration (modern versions should ask you whether you want to use local::lib on initial configuration), and cpanm doesn't need any extra configuration; I'd recommend the latter.

Of course, you could just install an entire build of Perl locally using perlbrew.