I have been using PostgreSQL 8.2.3 under Redhat Enterprise Linux AS 4, but when I tried to install the postgresql-plperl RPM I got a sequence of dependency failures, and remedying them got me into an apparently infinite loop of dependencies on libpq.so versions.
Try grabbing all the PostgreSQL RPMS for 8.2.3/RHEL AS4 from http://www.postgresql.org/ftp/binary/v8.2.3/linux/rpms/redhat/rhel-as-4/ (there's also directories for Itanium 64 and x86 64, so know what processor type you're using and adjust as needed). Often RPM dependency confusions can be got around through specifying more than one .rpm at once. Also try upgrading with rpm -Uvh rather than rpm -i So if you grab the RPMS you need from there and install them all at once, you should be fine. Good luck, Stuart.