@icesteruk: typing in "lua display(package.loaded)" in the Mudlet command line will show pretty much everything that the lua system has stored, including lua system libraries such as the lua file system library a.k.a. "lfs"), the "global" table "_G", the lua commands that Mudlet provides for you (mainly coded in the, um, somewhat meaty source ./src/TLuaInterpreter.cpp file). Needless to say, removing the wrong thing, by setting the value to nil and allowing the garbage collection to do its work, can stop things from working, so the other posters' systems have ways of "blacklisting" or otherwise telling their code "please don't touch those things"...