The formal definition of a version of Perl 6 corresponds to (a frozen version of) the Perl 6 test suite (currently around 120K unit tests). A compiler declares

The formal definition of a version of Perl 6 corresponds to (a frozen version of) the Perl 6 test suite (currently around 120K unit tests). A compiler declares its claimed compliance by reference to these test suites: > perl6 -v This is Rakudo version 2016.01.1 built on MoarVM version 2016.01 implementing Perl 6.c. 6.c labels a frozen version of the Perl 6 test suite and thus a version of the Perl 6 language. All serious users of the language are encouraged to check/improve the language test suite to ensure it covers what they want covered in either an existing version or an upcoming one.