fn:in-scope-prefixes

[David Carlisle]

your code looks OK although a bit scary for something that's a
one-liner in xslt, I think an xquery analogue of xsl:copy ought to be
pretty high on the xquery 1.x wish list!

As others have said I don't think that in-scope-prefixes can ever return
duplicate strings, and your code worked (with saxon) on the example you
posted.

David