Good point. That's the drawback where edge-cases can add a lot of complexity.
Perhaps throw an exception? Allow annotations on how to resolve (see below)? Implicit rules? — down the rabbit hole of smart-matching :(

Example: Resolve overloaded @{} by using the standard notation as a hint like so?

$it->@( $key [$idx] section $i some.doc method1() sub1(5) method2($x) 
+);
[download]