I have emailed the author. I would like to offer a patch but I am not sure what the problem is. I was in a hurry to get my project complete so I could go to sleep.

A good reason to use Geo::Distance::XS

First, thanks! I admit that I didn't try it for a few reasons. The first is that I assumed one was just an XS implementation of the other to include the bug. The second reason is that in the environment where this needed to run, XS is not an easy option. Without going into a lot of detail - local politics have created technical hurdles I didn't want to jump through (I was tired). It is also the reason I didn't use GIS::Distance. I was pretty sure (and you confirmed) that it produces correct results but the litany of dependencies without an internet connection was unreasonable.

I am happy that there are working solutions out there. I guess after reflecting on my lamentation, what I really should have asked is: Does anyone know of a Geo::Distance::Lite that works?

Regarding your benchmark. First, I suspect you didn't "You can stick with the pure Perl version by setting the GEO_DISTANCE_PP environment variable before using this module" This is because Geo::Distance gave the correct answer which it I know it doesn't (the point of this thread). Second, it would only be fair to add tye's version which avoids the whole OO overhead.