// Pulse light's range between original range
// and half of the original one

var duration : float = 3.0;
private var originalRange : float;
originalRange = light.range;

function Update() {
    var amplitude : float = Mathf.PingPong( Time.time, duration );
    // transform from 0..duration to 0.5..1 range
    amplitude = amplitude / duration * 0.5 + 0.5;
    // set light range
    light.range = originalRange * amplitude;
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public float duration = 3.0F;
    private float originalRange;
    void Update() {
        float amplitude = Mathf.PingPong(Time.time, duration);
        amplitude = amplitude / duration * 0.5F + 0.5F;
        light.range = originalRange * amplitude;
    }
    void Example() {
        originalRange = light.range;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public duration as single = 3.0F

    private originalRange as single

    def Update():
        amplitude as single = Mathf.PingPong(Time.time, duration)
        amplitude = (((amplitude / duration) * 0.5F) + 0.5F)
        light.range = (originalRange * amplitude)

    def Example():
        originalRange = light.range