// Prints Option or Alt key was pressed depending the
// platform this script is being run.
function OnGUI() {
var e : Event = Event.current;
if (e.alt) {
if(Application.platform == RuntimePlatform.OSXEditor) {
Debug.Log("Option key was pressed");
} else if( Application.platform == RuntimePlatform.WindowsEditor) {
Debug.Log("Alt Key was pressed!");
}
}
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void OnGUI() {
Event e = Event.current;
if (e.alt)
if (Application.platform == RuntimePlatform.OSXEditor)
Debug.Log("Option key was pressed");
else
if (Application.platform == RuntimePlatform.WindowsEditor)
Debug.Log("Alt Key was pressed!");


}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def OnGUI():
e as Event = Event.current
if e.alt:
if Application.platform == RuntimePlatform.OSXEditor:
Debug.Log('Option key was pressed')
elif Application.platform == RuntimePlatform.WindowsEditor:
Debug.Log('Alt Key was pressed!')