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's pretty much it.

The third example shows the so-called auto-threading behavior. I think it's significantly different than what you can do with sets.

A Junction in Perl 6 is "a superposition of data values pretending to be a single value". So for instance any algebraic expression can be used with a junction as if it was a scalar. The result will be a junction.

In this example the expression is $_ %% 2, which is Perl 6's way of writing the boolean statement "the variable $_ is divisible by 2". We use this expression with ($a & $b) instead of $_.

The third seems to be shorthand for map and reduce (or only reduce).

In Ruby, you could express the same with `[2,4,6].reduce(true) {|even,num| even & num.even? }` or more clearer IMO `[2,4,6].map(&:even?).reduce(&:&)`.