The history of luaTEX 2006–2009 / v 0.50 - Pragma ADE

tex.print("access")
else
tex.print("no access")
end
tex.print(global.characters.data[0xA9].contextname)
\stopusercode
This gives: ‘user 1 user 2 no access copyright’.
If you're writing a module, you might want to reserve a private namespace. This is done
with:
\definenamedlua[mymodule][my interesting module]
Now we can say:
\startmymodulecode
help = { "help" }
tex.print(help[1])
\stopmymodulecode
This gives: ‘help’. The information is remembered:
\startmymodulecode
tex.print(help[1])
\stopmymodulecode
Indeed we get: ‘help’.
Just to check the isolation we try:
\startusercode
tex.print(help and help[1] or "no help")
\stopusercode
As expected this gives: ‘no help’ but when we do the following we will get an error message:
\startusercode
tex.print(help[1])
\stopusercode
! LuaTeX error :2: attempt to index global
'help' (a nil value)
stack traceback:
:2: in main chunk.
298 User code