Perl doesn't have "native" support for PostgreSQL. It doesn't even have DBI stuff natively. You use DBI, which is a library that abstracts out database stuff, then behind that layer are "drivers" for each database (like PostgreSQL, MySQL, etc..). The drivers are called DBD, like DBD::Pg for PostgreSQL. But you don't use those drivers directly from your code; rather, you use DBI which sits in front of the drivers.

But anyway, DBI can't be found. That means either it's not installed or isn't in the %INC path. So look for it with `locate DBI`. If you have to install it, use CPAN (as root type `cpan`, or maybe `perl -MCPAN -eshell`, then `install DBI` and `install DBD::Pg`. If you found DBI installed, then you might have to do something like "use lib '/path/to/DBI/'". So first, see if DBI is installed.