Answer: net-snmp-perl and Net::SNMP are two different things.
net-snmp-perl is the Perl bindings for the SNMP library at:
http://net-snmp.sourceforge.net/
which provides an SNMP.pm without the Net:: prefix.
Net::SNMP is a Perl module from
http://search.cpan.org/dist/Net-SNMP/
which provides Net::SNMP (i.e. it would be /usr/lib/perl5/vendor_perl/5.8.5/Net/SNMP.pm
).
You can find RPM for this package in Dag’s repo:
http://dag.wieers.com/packages/perl-Net-SNMP/
UPDATE: With Pandora FMS 3.0 this library is not needed anymore.