Using PL/pgSQL

I'm trying to install PL/pgSQL so that I can use it in a FUNCTION. I'm
using PostGres 6.5.x (I know I need to upgrade...but that is another
subject...). So far I've done the following:
create function pgpgsql_call_handler() returns opaque as
'/usr/local/pgsql/lib/plpgsql.so' language 'C';
create procedural language 'plpgsql' handler plpgsql_call_handler
lancompiler 'PL/pgSQL';

I get a successful creation with these...
When I try and execute a function that uses "language 'plpgsql'", I get
the following error:

ERROR: Load of file /usr/local/pgsql/lib/plpgsql.so failed: dlopen
'/usr/local/pgsql/lib/plpgsql.so' failed. (Shared object"libpq.so.2"
not found)

I have verified that these 2 files do exist in the
/usr/local/pgsql/lib/ directory. Their permissions are both rw-r--r--
and owned by pgsql:pgsql

Thoughts?