const int switchPin = 2;// the port of the pushbutton pin
const int ledPin =  13;// the port of the LED pin

boolean lastButton = LOW;
boolean currentButton = LOW;
boolean ledOn = false;

void setup() 
{
  pinMode(ledPin, OUTPUT);
  pinMode(switchPin, INPUT);
}

boolean debounce(boolean last)
{
  boolean current = digitalRead(switchPin);
  if (last != current)
  {
    delay(5);
    current = digitalRead(switchPin);
  }
  return current;
}

void loop() 
{
  currentButton = debounce(lastButton);
  if (lastButton == LOW && currentButton == HIGH)
  {
    ledOn = !ledOn;
  }
  lastButton = currentButton; 
  digitalWrite(ledPin, ledOn);
}