A nice environmental module style for 5.2

gistfile1.lua

--takes the environment to encapsulate
local function modme(encenv)
  local retmod = {}
  local envmt = {}
  function envmt.__index(t, k)
    return retmod[k] or encenv[k]
  end
  function envmt.__newindex(t, k, v)
    retmod[k] = v
  end
end

local _ENV, retmod = modme(_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 --

return retmod