Short example for installing DBD-Pg-0.93 (assuming your installed
postgres under /usr/local/pgsql).

export POSTGRES_INCLUDE=/usr/local/pgsql/include
export POSTGRES_LIB=/usr/local/pgsql/lib
export DBI_DB=Pg DBI_DSN=dbi:Og:dbname=test DBI_USER=test DBI_PASS=toto55
perl Makefile.PL
make all
make install