You will notice that there are include statements in the above illustration and if you change these, you won't be able to compile the project. Lets now exclude all include references. By doing so we won't have to change any file names and can filter for symbols only. We will do so by using regular expressions. Regular expressions (regex) are a powerful means to specify patterns for filters and search strings in the various SNiFF+ tools, especially in the Retriever. Basically, regular expressions are a system of matching character patterns. For more information, please see Reference Guide -- Regular Expressions.