local roomNow = "room1";
local cave = {
  ["room1"] = {["south"] = "room3", ["east"] = "room2"}, --room1 - open south (r3), east (r2)
  ["room2"] = {["south"] = "room4", ["west"] = "room1"}, --room2 - open south (r4), west (r1)
  ["room3"] = {["north"] = "room1", ["east"] = "room4"}, --room3 - open north (r1), east (r4)
  ["room4"] = {} --room4 - won game
};

local gameloop = function(where, room)
  print("You are in " .. room .. ". Where you go?");
  local nextRoom = io.read();
  local check = where[room][nextRoom];
  check = check and check or room;
  if check == room then
    print("Wrong move");
  end;
  return check;
end

repeat
  roomNow = gameloop(cave, roomNow);
until roomNow == "room4";
print("Congratulations, you won!");