Classic style 5.2 environmental module function

gistfile1.lua

--has the same signature as classic module (almost)
local function module(name, encenv)
  local mod_t = {}
  local envmt = {}

  function envmt.__index(t, k)
    return mod_t[k] or encenv[k]
  end
  function envmt.__newindex(t, k, v)
    mod_t[k] = v
  end

  package.loaded[name] = mod_t
  return envmt
end

--this is the line that would go at the top of a module
local _ENV = module(..., _ENV)

-- all environment variables created here go into the module --
-- all environment variables read here read from the module --
-- if not present, they read from the encapsulating env --
-- the returned module does not provide access to the environment --