simple contains assertion with regular expression in groovy

Hi, I am using a soap ui pro. I am having trouble set the contains assertion to regular expression.

def b = testRunner.testCase.getTestStepByName("Test1")

def ast = b.addAssertion("Contains")
ast.setToken("Ferdinand.*Confuse")

what should I do next so that the assertion will evaluate it as a regular expression?

Thanks,
Ferdinand