OK, I will use external files next time. In this quick-and-dirty
approach I just added string.format since it was easier than
restructuring everything.

I thought that \startluacode should be behaving the same way as
verbatim environments where commands inside verbatim have no
influence, but apparently I was wrong.
I also think so.
Can be strange, but inside a \startluacode\stopluacode I have no problems to think at -- as comment
while I have problems to think to % as comment

And put lua code in a separate  file not always  is a good solution


--
luigi