Your modul will follow the nearest modul

modul follow()

// follow
var activeFollow = false;
function follow(){
  var siblingModuls = modul.sonar();
  var c = modul.coordinates();
  if(siblingModuls.length === 0){
    ui.log("You seem alone…");    
  }else{
    var modul1 = siblingModuls[0];
    var mc = modul1.coordinates();
    var mx = mc[0];
    var my = mc[1];
    if (c[0]-1 > mx) {
      modul.move("left");
    } else if (c[0]+1 < mx) {
      modul.move("right");
    }
    if (c[1]-1 > my) {
      modul.move("top");
    } else if (c[1]+1 < my) {
      modul.move("bottom");
    }
  }
}
function initFollow() {
  activeFollow = true;
}
function stopFollow() {
  activeFollow = false;
}

// Don’t forget to call the function each world’s time
world.on('interval', function(){
  if (activeFollow) follow();
});

// …and buttons
var actionsPanel = ui.buttonsPanel("Actions", [
  ui.button("follow", initFollow),
  ui.button("stopFollow", stopFollow)
]);