out of memory for query result

I am trying to select a result set from a 2-table join, which should be
returning 5,045,358 rows. I receive this error:

DBD::Pg::st execute failed: out of memory for query result

I am using Perl with DBI cursor (so i think) to retreive the data
(prepare, execute, fetchrow_hashref, ..., finish). Perhaps either the
DBD or libpq or something is buffering the result and not passing
individual rows from the server (which runs on the same server as the
application).

I am using Postgres 7.4.7, under 4.11-RELEASE FreeBSD 4.11-RELEASE using
perl v5.8.6 and DBD-Pg-1.32_1.

Any suggestions on how to avoid this? Should i be using the API
differently with Perl?

Thanks,
Allen