Experimental Rule Engine HTTP Post

Hey. I just wanted to use the experimental Rule Engine.
Some simple Rules work very well, so I needed to go a step further.

I wanted to use the scripted Action and execute there some javascript code, especially a HTTP Post.
When I tried to use the XMLHttpRequest Element in the Script. I got a failure:
Script execution failed: ReferenceError: “XMLHttpRequest” is not defined in at line number 1

Has someone of you experiences with something like that?