libpq dependencies

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. I had versions 3 and 4 in
/usr/lib and version 5 in /usr/local/pgsql/lib, but posgresql-libs still
reported it needed version 3 and couldn't find it. So I installed
compat-postgresql-libs-3-3PGDG and tried again. Now postgresql-libs
complains it can't find version 4.

I haven't found any comprehensive guide to shared library problems
associated with PostgreSQL, and it's a shame, since everything else about
PostgreSQL seems excellently documented.

I've given up, and decided to return to Redhat's somewhat older version.
It installs itself from Red Hat Network without any errors, and I probably
won't get library incompatibilities when doing future updates.