One of the most useful parts of perl is probably its facility for using regular expressions. Regular expressions are little bits of code that describe a piece of text. Perl is not alone in its use of regular expressions. In fact they are so useful that most computer langauges either have them build in or have regular expression libraries build for them. What is presented here is only a miniscule subset of what can be done with regular expressions, but whole books could be written on them (in fact one has - see the references). You will definitely want to learn more about regular expressions as you start to use Perl.