Please see complete documentation at http://search.cpan.org/dist/local-lib/lib/local/lib.pm.
To get started you will just need to know that everything by default will be installed into your ~/perl5 directory. You can install a module calling the right version of perl in this case by the following (in this example /opt/local/stow/perl-5.14.2/bin/perl).
/opt/local/stow/perl-5.14.2/bin/perl -MCPAN -Mlocal::lib -e 'CPAN::install(LWP)'
You will need to then make perl aware of this alternate location for perl modules. You will need to run and copy the output that emits out of this command into your shell intialization files (.cshrc/.tcshrc, .bash_profile, etc..).
You will then need to log out/log in or source your dot files to get the new variables.