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.