gistfile1.txt

local funtab=setmetatable({}, {__mode="k",__index=function(t,k) t[k]={}; return t[k] end})
debug.setmetatable(function() end, {
  __index=function(f,k)
    return funtab[f][k]
  end,
  __newindex=function(f,k,v)
    funtab[f][k] = v
  end
});

local function this()
  return debug.getinfo(2,"f").func
end

function f()
  print(this().x)
end

f.x = 1234

f()