Rakudo::Slippy::Semilist

Implements postcircumfix:<{|| }> to allow coercion of Array to semilist. Implements postcircumfix:<{; }>:exists and postcircumfix:<{|| }>. see: http://design.perl6.org/S09.html#line_419

Usage:

use Rakudo::Slippy::Semilist;

my @a = 1,2,3;
my %h;
%h{||@a} = 42;
dd %h;
# OUTPUT«Hash %h = {"1" => ${"2" => ${"3" => 1}}}␤»
dd %h{1;2;3}:exists;
# OUTPUT«Bool::True␤»