Development of the Perl 5 language is covered by the Standards of Conduct in the perlpolicy document. (See pod/perlpolicy.pod for source version.)
The overarching rule is that participants are expected to be civil. It is not enough to be factual. You must also be civil.
The Standard of Conduct falls under the authority of the Perl Steering Council and covers activities on the perl5-porters mailing list, the GitHub repository issue/pull-request tracker, and any other venues directly organized on behalf the Perl Steering Council.
NOTE: The Perl Steering Council operates independently of The Perl Foundation and other Perl community organizations. Consult their websites for information on other community codes of conduct.