add perl as a supported language

[luto]

As we have perl-core (the set of standard Perl modules) and perl-App-cpanminus (a modern package manager) installed, our Perl setup is usable for most tasks. We need some documentation for it.

• Versioning: Explain why we offer Perl 5.16 despite it being already end-of-life (but gets backported updates by Red Hat)
• Refer to perlbrew as an alternative to install your completely own (and thus unsupported) Perl
• Explain cpanm to install Perl modules from CPAN
• If user-installed modules are used, a single line has to be added to the .bashrc - but we should probably do this centrally on our side
• Apart from the docs we can write a guide or two on how to create a basic application with the Catalyst or Mojolicious framework

[noave]

it is already documented but could be extended: https://manual.uberspace.de/lang-perl/