Straightforward solution:

    function g(o)
      if o then return "gal" end
      o = "o"
      local function go(al)
        if al then
          return "g"..o..al
        else
          o = o .. "o"
          return go
        end
      end
      return go
    end
    print(g()('al'))

More amusing and hackish solution:

    setmetatable(_G, -- or _ENV, but maintain 5.1 compatibility
      { __index = function(_, g)
        local o = ""
        local function go(al)
          if al then
            return g..o..al
          end
          o = o.."o"
          return go
        end
        return go
      end})
    print(g()('al'))
    print(G()'al')
    print(Wh()()'pdedo')