I get the error message "stdin:1: '<name>' expected near 'end'", others index name (for example, a.end1=2, a.b=2 ) are ok.
Looks like only "end" given error message.
'end' is a lua keyword. You'd get the same error with 'if', 'for', 'do', and so on. In these cases, you can't use the 'tbl.key' syntax, you have to use 'tbl["key"]' instead.
