The extension is not mandatory.   Usually people use .p6, but you can also use .pl  .  Notice that I&#x27;ve never seen .pl6.<p>&#x27;use v6;&#x27; is not mandatory either, but it allows your program to display an helpful error message if you try to run it with the perl 5 interpreter.  Try &quot;perl -e &#x27;use v6;&#x27;&quot;, you should get:<p><pre><code>    Perl v6.0.0 required--this is only v5.20.2, stopped at -e line 1.
    BEGIN failed--compilation aborted at -e line 1.
</code></pre>
&#x27;use v2;&#x27; will not run with the Perl 6 interpreter, but &#x27;use v5;&#x27; will work, as the Perl 6 interpreter is specced to be able to run Perl 5, albeit with certain limitations (no XS, for instance).