// prints inside when mouse is in lower left corner

function Update () {
    var rect = Rect (0, 0, 150, 150);
    if (rect.Contains(Input.mousePosition))
        print("Inside");
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Update() {
        Rect rect = new Rect(0, 0, 150, 150);
        if (rect.Contains(Input.mousePosition))
            print("Inside");
        
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Update():
        rect as Rect = Rect(0, 0, 150, 150)
        if rect.Contains(Input.mousePosition):
            print('Inside')