anchor.diff:  
   -- check for combination/required flags
   local function check_flags()
  -	if not P_SET then
  -		die("Missing required parameter /P")
  -	end
   	if INSTALL_LUA then
   		if vars.LUA_INCDIR or vars.LUA_BINDIR or vars.LUA_LIBDIR or vars.LUA_PREFIX then
   			die("Cannot combine option /L with any of /LUA /BIN /LIB /INC")
  
positive.code: 
  Other options:
  /CONFIG [dir]  Location where the config file should be installed.
                 Default is same place of installation
  /FORCECONFIG   Use a single config location. Do not use the
                 LUAROCKS_CONFIG variable or the user's home directory.
                 Useful to avoid conflicts when LuaRocks
  
negative.code: vars.LUA_RUNTIME = nil
  vars.UNAME_M = nil
  
  local FORCE = false
  local FORCE_CONFIG = false
  local INSTALL_LUA = false
  local USE_MINGW = false
  local REGISTRY = false
  local NOADMIN = false
  local PROMPT = true
  
  ---
  -- Some helpers
  