How to concatenate two Sets of strings in Perl 6?

Question

Is there an idiomatic way or a built-in method to concatenate two Sets of strings?

Here's what I want:

> my Set $left = <start_ begin_>.Set
set(begin_ start_)
> my Set $right = <end finish>.Set
set(end finish)
> my Set $left_right = ($left.keys X~ $right.keys).Set
set(begin_end begin_finish start_end start_finish)

Or, if there are more than two of them:

> my Set $middle = <center_ base_>.Set
> my Set $all = ([X~] $left.keys, $middle.keys, $right.keys).Set
set(begin_base_end begin_base_finish begin_center_end begin_center_finish start_base_end start_base_finish start_center_end start_center_finish)

Answer 1

You can use the reduce function to go from an arbitrary number of sets to a single set with everything concatenated in it:

my Set @sets = set(<start_ begin_>),
               set(<center_ base_>),
               set(<end finish>);
my $result = @sets.reduce({ set $^a.keys X~ $^b.keys });
say $result.perl
# =>
Set.new("start_base_end","begin_center_finish","start_center_finish",
        "start_center_end","start_base_finish","begin_base_end",
        "begin_center_end","begin_base_finish")

That seems clean to me.