What does _UPVALUEX_ mean in my code?

Hi, 

Here’s the code:

local L0\_0 L0\_0 = module L0\_0((...), package.seeall) function L0\_0(A0\_1) if A0\_1 - math.floor(A0\_1) \> 0 then error("trying to use bitwise operation on non-integer!") end end bit = { bxor = function(A0\_17, A1\_18) local L2\_19, L3\_20, L4\_21, L5\_22 L2\_19 = \_UPVALUE0\_ L3\_20 = A0\_17 L2\_19 = L2\_19(L3\_20) L3\_20 = \_UPVALUE0\_ L4\_21 = A1\_18 L3\_20 = L3\_20(L4\_21) L4\_21 = \_UPVALUE1\_ L5\_22 = L2\_19 L4\_21(L5\_22, L3\_20) L4\_21 = {} L5\_22 = math L5\_22 = L5\_22.max L5\_22 = L5\_22(table.getn(L2\_19), table.getn(L3\_20)) for \_FORV\_9\_ = 1, L5\_22 do if L2\_19[\_FORV\_9\_] ~= L3\_20[\_FORV\_9\_] then L4\_21[\_FORV\_9\_] = 1 else L4\_21[\_FORV\_9\_] = 0 end end return \_UPVALUE2\_(L4\_21) end }

I don’t understand what do these _UPVALUE0_, _UPVALUE1_ & _UPVALUE2_ mean. 

See this for reference:

http://valentin.dasdeck.com/lingo/lsw/editor_lingo_support/SciTE/SciTELingoIDE/lua_backend/bit.lua

See this for reference:

http://valentin.dasdeck.com/lingo/lsw/editor_lingo_support/SciTE/SciTELingoIDE/lua_backend/bit.lua