pi.util.String.format(string,arguments ...)
>>> var str = "Hello, {0}, you look {1} today!";
>>> pi.util.String.format(str,"Angelina Jolie","so sexy");
"Hello Mrs. Angeline Jolie, you look so sexy today!"
>>> pi.util.String.format(str,"Mr. Bush", "so dummy");
"Hello Mr. Bush, you look so dummy today!"