Language of extopenscad?

I've been using OpenSCAD for several years now and have gotten around many of the awkward aspects, but extopenscad is very appealing. The problem is that it is a very ill-specified "extended subset" of OpenSCAD with many things missing, many added, and many just working differently. For example, there is no hull() nor minkowski() -- two of the real workhorses in OpenSCAD -- and newer things, like specifying d=100 instead of r=50 in a cylinder also are not there. Semantic differences include things like setting $fn=6 globally having no impact on cylinders. I don't have a huge problem with things being different, but I have a big problem with the lack of a specification of the very-inappropriately-named extopenscad language. Is there a real, stable, language spec?

I don't have a huge problem with this language just being similar enough to OpenSCAD to make it easy for users to migrate designs, but it isn't really usable without a spec of what's there and how it works... especially given the lack of decent syntax error handling.