how would you detect the special comment?

eg, could you have a comment first?

(:hello world:)(:# xmlns:p=http://other/uri #:) /p:foo/p:bar[2]

and is this an error or just a normal comment (with therefore no
binding for the default xpath namespace).

(:# xmlns==http://other/uri #:) /foo/bar[2]
         ^

would the bindings have to be at the top? (cf xquery prolog) or could you
give them a local scope.

/(:# xmlns:p=http://other/uri #:) p:foo/(:# xmlns:p=http://yetother/uri #:)p:bar[2]


(just musing in public, I don't imply that these are necessarily
problems just that there are several possible answers well, two in each
case, yes or no...)

David