luaL_requiref[-0, +1, e]
void luaL_requiref (lua_State *L, const char *modname,
                    lua_CFunction openf, int glb);
 If modname is not already present in package.loaded, calls function openf with string modname as an argument and sets the call result in package.loaded[modname], as if that function has been called through require. 
 If glb is true, also stores the module into global modname. 
 Leaves a copy of the module on the stack.