In most cases you don't have to install it using rpm's (unless you are installing Perl modules to satisfy the dependancies of another rpm package) - you can install it using the CPAN shell, so you don't have to upgrade your core Perl installation.
As root, type perl -MCPAN -e shell
to start the CPAN shell. It will ask you quite a few questions to set up. When done, you can use the CPAN shell to install Perl modules.
Type install <modulename>
at the cpan>
prompt, like this for installing the Crypt::Rijndael module: install Crypt::Rijndael
. That's how simple it is.
To find and learn more about Perl modules you use the search.cpan.org
site, which is a real gem.