// Detects if the shift key was pressed
function OnGUI() {
var e : Event = Event.current;
if (e.shift) {
Debug.Log("Shift was pressed :O");
}
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void OnGUI() {
Event e = Event.current;
if (e.shift)
Debug.Log("Shift was pressed :O");

}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def OnGUI():
e as Event = Event.current
if e.shift:
Debug.Log('Shift was pressed :O')