S02 interpolation of entire hashes

[Dave Whipp]

The tests in S02 L<S02/Literal/In order to interpolate an entire hash> 
appear to assume that an interpolated hash renders its keys in a sorted 
order. But this property doesn't seem to be stated in the text. Is it 
true that the keys are always sorted for interpolation? (is it possible, 
in P6, for hash keys to not be comparable?)