Question

This function returns the name and the value of the local variable
with index local of the function at level level of the stack.
(The first parameter or local variable has index 1, and so on,
until the last active local variable.)
The function returns nil if there is no local
variable with the given index,
and raises an error when called with a level out of range.
(You can call debug.getinfo to check whether the level is valid.)

Variable names starting with '(' (open parentheses)
represent internal variables
(loop control variables, temporaries, and C function locals).