We can do whatever we like with \ since it's really a *macro* that imposes lvalue context (or at least, indirection in the abstract, if we were ever to allow it in an outer lvalue context). In the case of \($a,$b) it is also distributing that context over the items in the list without copying.
The only questions in my mind are whether Perl 5's \($a,$b) is what people expect (it's arguably counterintuitive to newbies), and whether there's some other construct that would more naturally construct a list of references. It's not just \« though, since it has to *parse* as a list of lvalues. Maybe a siglet can degenerate to that, but there are problems with that approach too. Unless someone can come up with a better proposal, \($a,$b) is the default winner on the basis of prior Perl 5 art. Larry