Ned has answered this nicely. I was thinking about substring matches (kind
of simplified :matches), but this can be thought of as an implementation
details. I.e. we can consider an external list to be black box.
I agree with Ned completely, and Alexey sums it up perfectly: an
external list is a black box. It was the lack of that semantic that
made me resistant to external lists before. If :list is a match type,
that major issue goes away for me (though I still have others, but I
think they can be resolved).
Barry