Hmm, both of you are kinda going off on a tangent here. The meaning of the Whatever represented by * is neither something that gets magically interpreted before postcircumfix:<[ ]>, nor is it a compile-time rewrite. Context is supplied by binding in Perl 6, and the binding happens within .. It's the fact that the parameter within . is declared with @@ that causes it to bind as a slice, so that each dimension of the argument comes in as a single array element.
(By the way, you'll note the utility of being able to talk about a postfix by saying ., which is one of the reasons we allow the optional dot there. :) Now, you'll ask how *-2 works. If you do math on a Whatever object, it just remembers that offset until the Whatever is given a meaning, which, in this case, is delayed until the subscripting operator decides what the size of the next dimension is. At a lower level than the subscript it probably ends up being some kind of a fallback multi that binds to a Whatever type for that dimension, as the subscripting operator processes through each dimension in its @@ array. Or maybe it's just a case in a switch. In any case, the subscriptor knows the next "top" dimension, so it can know the size at that point. At compile time the subscript parser really only knows how many dimensions are referred to by how many semicolons there are. A subscript that is explicitly cast to @@ is known to be multidimensional, and interpolates the returned List of Capture into the outer List of Capture, and the compiler can make no compile-time assumptions about how far down the dimension list any subsequent dimensional sublists will end up. However, at least we can hope that @@ x() specifies the exact number of dimensions to interpolate at run time. One additional variant of Whatever is **, which represents an arbitrary number of dimensions. In essence, it's an instruction to the subscripting logic as it's processing top-down through the dimensions that it has to reverse its logic and count the rest of the subscripts bottom-up from the end of its @@ bound list instead of from the beginning. As such, there can really only be one such reversal, so we limit ourselves to a single ** argument representing an arbitrary number of dimensions to skip over, assuming the rest of the dimensions are end-anchored, as it were. Larry