I've kept my work to the closest() method. I have made modifications to get it working properly with DBI. I also added the 'inner radius simplistic calculation' (see the to do list) but there are issues with it. Its not really a radius, but instead its an inscribed square. (The initial test is a circumscribed square). But the inner test cannot be used if you need the actual distances from the centerpoint, which would include sorting the results by distance.

I also added doing both the outer and inner optimizations for arrayref sources, again with the same distance caveat.

I am a mathematician by education, but have no formal training in non-euclidian geometry, so im wary about messing with the various distance calculations at this point.