By default Spock uses a match first algorithm to determine the defined return value of a method. So whenever there are multiple defined return values, it will pick the first (that is not exhausted). This change enables a user to change this to a match last algorithm. So Spock will pick the last defined return value (that is not exhausted). This enables easy overriding of default return values. As requested in issue spockframework#26, spockframework#251, spockframework#321 and spockframework#962.