The letter of the law is now "avoid creating names that start with an
underscore followed by one or more uppercase letters".
Note that the manual says to avoid *creating* such names, not using
them. For instance, everybody can use (and many people do) _ENV for
their onw variables in their programs, to do what it was created for.
If the Lua team "creates" the name _VERSION for module identification,
everybody could use it for that purpose. (I fully agree with Hisham that
it is not a good idea to use that name unless we have that first step.)
-- Roberto