list = {"hello world"}

idx = 0

io = {}

io.read = function()

  idx = idx+1

  return list[idx]

end

function allwords ()

  local line = io.read()  -- current line

  local pos = 1           -- current position in the line

  return function ()      -- iterator function

    while line do         -- repeat while there are lines

      local s, e = string.find(line, "%w+", pos)

      if s then           -- found a word?

        pos = e + 1       -- next position is after this word

        return string.sub(line, s, e)     -- return the word

      else

        line = io.read()  -- word not found; try next line

        pos = 1           -- restart from first position

      end

    end

    return nil            -- no more lines: end of traversal

  end

end

-- use example

for word in allwords() do

  print(word)

end