{ Block returning a code reference }->(); doesn't work, but ( Block returning a code reference )->(); works, doesn't it?

Also &$thingy calls the subroutine with the same @_, so it's not the same as $thingy->(), this latter is really equivalent to &$thingy(). I think you probably thought of &$thingy() anyway, as that's what's one character less than $thingy->().