http://www.lua.org/versions.html#5.1
I'll be updating IrrLua to Lua 5.1 once the other tools are also ported to Lua 5.1 (tolua++ in particular).The main features in Lua 5.1 are a new module system, incremental garbage collection, new mechanism for varargs, new syntax for long strings and comments, mod operator, length operator, metatables for all types, new configuration scheme via luaconf.h, fully reentrant parser, and more.