I'm not following what you are trying to do. Dreamhost does not reset @INC, its just that @INC is builtin (when the perl executable was compiled) and then when the perl executable runs, it checks environment variables OR the lib pragma.
Are you getting errors when trying to execute the perl script as CGI? If so, just open the script, and add
use lib '/home/username/.perllib';
For example, I have ~/lib/Company, and in my CGI scripts start with:
use lib '/home/username/lib';
Here is what the perl documentation says:
Perl / MySQL / HTML+CSS