"Be nice, all I know about Perl is how to spell it"

Don't worry, you're in the right place. I'm not a Solaris sysadmin, but our client insist on using it. Yes, 'modern' Solaris ships with a really old version of Perl (as you say 5.8.4, from 2004). As a perl developer who works primarily on Solaris on a daily basis I'd advise the following. Install gcc, install a modern perl elsewhere on your system (see INSTALL - installation prefix), e.g. /app/applicationname. Then the developer can just work away as normal, or as normal as you can on Solaris.

I'd suggest installing App::cpanminus to get cpanm, which is a faster tool for installing modules than cpan. If your developer is going to be installing/updating cpan modules fairly regularly this will make things easier. If this server does not have internet access, you can create a portable mini cpan mirror on a machine which does have internet access, using the minicpan tool.