If its a job interview, as opposed to a school test, it should be "open book". Ask to have your laptop full of your old test code snippets, review all the perldocs before going in, so you can quickly pull up the right perldoc. Don't forget the "perldoc -q somtopic" , like "perldoc -q file" which will search all the perlfaqs for entries with the topic in it...... a great source of answers.
Also remember, if you are allowed live internet connection during the interview, search google and groups.google for all sorts of previously written code and answers.