// detects when the other transform is closer than closeDistance
// this is faster than using Vector3.magnitude

var other : Transform;
var closeDistance = 5.0;

function Update() {
    if (other) {
        var sqrLen = (other.position - transform.position).sqrMagnitude;
        // square the distance we compare with
        if( sqrLen < closeDistance*closeDistance )
            print ("The other transform is close to me!");
    }
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public Transform other;
    public float closeDistance = 5.0F;
    void Update() {
        if (other) {
            float sqrLen = other.position - transform.position.sqrMagnitude;
            if (sqrLen < closeDistance * closeDistance)
                print("The other transform is close to me!");
            
        }
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public other as Transform

    public closeDistance as single = 5.0F

    def Update():
        if other:
            sqrLen as single = (other.position - transform.position).sqrMagnitude
            if sqrLen < (closeDistance * closeDistance):
                print('The other transform is close to me!')