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

...userdata")
tex.print(help[1])
}
An even more isolated variant is:
\startisolatedcode
help = { "help" }
tex.print(help and help[1] or "no help")
\stopisolatedcode
We get: ‘help’, while
\startisolatedcode
tex.print(help and help[1] or "no help")
\stopisolatedcode
gives: ‘no help’.
You can get access to the global data of other named code blocks by using the global
prex. At that level you have also access to the instances, but this time we append data,
so user has a table userdata:
For convenience we have made tex as well as some Lua tables directly accessible within
an instance. However, we recommend not to extend these yourself (even if we do it in
the core of MkIV).
User code 299