striplong

It would be nice if striplong worked, but the example fails when string.striplong is used in place of string.strip. The log says:

! LuaTeX error [string "\directlua "]:1: attempt to call field 'striplong' (a nil value)
stack traceback:
    [string "\directlua "]:1: in main chunk.

Is the format of the call different than shown in the wiki, or is a different mechanism required to quote a potentially long string?