Crossvrowser Userscript pattern

// ==UserScript==
// @name myUserJS
// @description My first crossbrowser userscript
// @author Mr_Mig
// @license MIT
// @version 1.0
// @include http://userscripts.org/*
// ==/UserScript==

// wrap the script in a closure (opera, ie)
// do not spoil the global scope
// The script can be transformed into a bookmarklet easily :)
(function(window, undefined ) {

    // normalized window
    var w;
    if (unsafeWindow != "undefined"){
        w = unsafeWindow
    } else {
        w = window;
    }

    // You can inject almost any javascript library here.
    // Just pass the w as the window reference,
        // e.g. jquery.min.js embedding:
    // (function(a,b){function ci(a) ... a.jQuery=a.$=d})(w);


    // do not run in frames
    if (w.self != w.top){
        return;
    }

    // additional url check.
    // Google Chrome do not treat @match as intended sometimes.
    if (/http:\/\/userscripts.org/.test(w.location.href)){
        //Below is the userscript code itself


        alert("Hello from the userscript");
    }
})(window);