I usually set just 3 things:

1. the PERL5LIB environment variable, the value should be something like /home/choroba/perl5/lib/perl5:/home/choroba/perl5/lib/perl5/ARCH, where ARCH comes from perl -MConfig -le 'print $Config{archname}'
2. mbuildpl_arg => q[--install-base=/home/choroba/perl5] in cpan (o conf)
3. makepl_arg   => q[INSTALL_BASE=/home/choroba/perl5] in cpan