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).<p>A compiler declares its claimed compliance by reference to these test suites:<p><pre><code>  &gt; perl6 -v
  This is Rakudo version 2016.01.1
  built on MoarVM version 2016.01
  implementing Perl 6.c.
</code></pre>
6.c labels a frozen version of the Perl 6 test suite and thus a version of the Perl 6 language.<p>All serious users of the language are encouraged to check&#x2F;improve the language test suite to ensure it covers what they want covered in either an existing version or an upcoming one.