Event.shift
var shift: bool;
bool shift;
shift as bool
Description

Is Shift held down? (Read Only)

Returns true if any Shift key is held down.
	// 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

public class Example(MonoBehaviour):

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