Lua 5.2: userdata environment tables gone?

[Josh Haberman <haberman@...>]

I hadn't been tracking the Lua 5.2 changes too closely, but I just noticed that lua_getfenv()/lua_setfenv() are gone.  I had been using userdata environment tables as a way of letting a userdata reference other Lua values.  I had previously been advised that giving each userdata its own metatable and mutating those metatables frequently would have bad performance consequences (see http://lua-users.org/lists/lua-l/2011-04/msg00319.html)

What's the Lua 5.2 way of letting a userdata contain references to other Lua values?

Thanks,

Josh