How do you create a pop up using Groovy script?

Now that we are making progress with using Groovy scripts I have a simple question that does not seem to be addressed anywhere in the manuals or sample text.

What is the syntax to perform a simple Pop Up with a message (Like "HelloWorld" PX) to the user when the script runs? Seems like everything points to using the History Tab or logMonitor.

That is rather obscure and we want to present the user with immediate feedback when they do something wrong, not wait for them to figure out it is buried in with all the other minutia in the History Tab.