On the one hand, by (interpreter compile-time) default, all numeric values in Lua are floats, and xor on floats doesn't make a lot of sense. On the other hand, given the popularity of embedded Lua (in which case the numeric type is probably int) the lack of bitwise operators gets frustrating. Actually I can attest to this, having used Lua in an embedded context.
Actually, by default numeric values are doubles, which can easily handle a 32-bit int without losing precision. And as I posted above, the Lua bitop library (which is standard in LuaJIT and Lua 5.2) gives you bitwise operations.
I did use bitop extensively. Having every bitwise operation be a function call was not as pleasant to type (or read) as dedicated bitwise operators but it did get the job done.
