For example, assume we want the folder structure series/series_index — title, with the caveat that if series does not exist, then the title should be in the top folder. Note that the ‘structure’ option allows the script to return HTML. Your error handling script can examine the error and take various actions depending on the error. You’ll find examples of how to use these variables throughout this chapter. 13.2.2. String Expressions String expressions allow you to easily mix path expressions with text.