You've gotten a pile of great answers. :) I'll add another to the pile, but omit explanation.
say % = ["foo" => "bar"], "baz" => 42; # {foo bar => baz => 42} say % = ["foo" => "bar"]; # {foo => bar} say % = ["foo" => "bar"],; # Odd number ... Only saw: $[:foo("bar")] -- raiph