class Foo
  attr_reader :bar

  def bar=(value)
    @bar = value + 2
  end
end

foo = Foo.new
foo.bar = 4

puts foo.bar

###


class Foo {
    has $.bar;

    method bar is rw {
        $!bar += 2;
        $!bar
    }
}

my $foo = Foo.new;
$foo.bar = 4;
say $foo.bar;