Control commands determine whether a block of actions are executed, or if no further actions should execute. Control keywords are positioned with an associated test command before the opening brace in a block to help control the order of execution through the policy script. Note that tests are covered further in the next section of the tutorial. For now, understand that a test command evaluates to either "true" or "false". The PureMessage policy.siv script uses three control keywords to filter messages: if, else, and stop.