By set operations I was more specifically thinking of intersection and union.  Testing if an element belongs to a set can indeed be done with junctions but that&#x27;s pretty much it.<p>The third example shows the so-called <i>auto-threading</i> behavior.  I think it&#x27;s significantly different than what you can do with sets.<p>A Junction in Perl 6 is &quot;a superposition of data values pretending to be a single value&quot;.  So for instance any algebraic expression can be used with a junction as if it was a scalar.  The result will be a junction.<p>In this example the expression is $_ %% 2, which is Perl 6&#x27;s way of writing the boolean statement &quot;the variable $_ is divisible by 2&quot;.  We use this expression with ($a &amp; $b) instead of $_.