RegExp.input, RegExp.leftContext, ...

I found this in felgall's page. I added script tag

<script type="text/javascript">

var re = /(t)he/g;
var mystring = "Over the moon.";
re.text(mystring);
alert(RegExp.input); // or RegExp.$_
alert(RegExp.leftContext); // or RegExp["$`"]
alert(RegExp.rightContext); // or RegExp["$'"]
alert(RegExp.lastMatch); // or RegExp["$&"]
alert(RegExp.lastParen); // or RegExp["$+"]
alert(re.source);

</script>

I don't see message box. Please tell me what I can do.