how to write xml to a popup window?

I want the browser to pop up a new window where xml content is written to and displayed. I can do it on the server side with perl. I try to do the same on the client side with JavaScript, but so far it is always HTML. Can this be done?

From everywhere I read, the answer is that I should use document.open("text/xml"), but it still shows up as html, has anyone tried and got it working?