On a server with CPanel, you can log into the WHM and install it there. If for some reason doesn’t work for you, you can log into the shell as root and install it via the command line. Once logged in, from any directory, type:
echo "HTML::Template" | /usr/local/cpanel/whostmgr/bin/perlmod -i
(in this case, the module we want to install is HTML::Template).
On a RedHat server, you can install it with up2date if you know the name of the RPM. If you don’t know it you can run
up2date --showall | grep -i perl
Then select the RPM you want and install it via up2date.
If the module you want still isn’t present you can install it manually via CPAN. Note that these modules are completely unsupported. If you wish to procede with the installation you can interactively install the module by running
perl -MCPAN -e shell
For example if you wanted to install Time::HiRes you would type
on the CPAN prompt.