First attempt at lua grammar...

lua.kpeg

%% name = Lupin::Parser

chunk = (stat ";"?)* (laststat ";"?)?

block = chunk

stat = varlist "=" explist |
      functioncall |
      "do" block "end" |
      "while" exp "do" block "end" |
      "repeat" block "until" exp |
      "if" exp "then" block ("elseif" exp "then" block)* ("else" block)? "end" |
      "for" name "=" exp "," exp ("," exp)? "do" block "end" |
      "for" namelist "in" explist "do" block "end" |
      "function" funcname funcbody |
      "local" "function" name funcbody |
      "local" namelist ("=" explist)?

laststat = "return" (explist)* | "break"

funcname = name ("." name)* (":" name)?

varlist = var ("," var)
var = name | prefixexp "[" exp "]" | prefixexp "." name

namelist = name ("," name)*

explist = (exp ",")* exp
exp = "nil" | "false" | "true" | number | string | "..." | function | prefixexp |
     tableconstructor | exp binop exp | unop exp

prefixexp = var | functioncall | "(" exp ")"

functioncall = prefixexps args | prefixexp ":" name args

args = "(" (explist)? ")" | tableconstructor | string

function = function funcbody
funcbody = "(" (parlist)? ")" block "end"

parlist = namelist ("," "...") | "..."

tableconstructor = "{" fieldlist "}"
fieldlist = field (fieldsep field)* (fieldsep)?
field = "[" exp "]" "=" exp | name "=" exp | exp
fieldsep = "," | ";"

binop = "+" | "-" | "*" | "/" | "^" | "%" | ".." | "<" | "<=" | ">" | ">=" | "==" | "~=" | "and" | "or"

unop = "-" | "not" | "#" 

root = chunk