The preceding discussion on regular expressions is really much too brief, but it would really require a complete new tutorial to fully desctibe regular expressions in Perl (or any other language, for that matter). Nevertheless, there is much more information online about regular expressions, or you can check out some of the references to see what they have to say about them (much more than I've said).
Nevertheless, this section should have given you at least a glimpse of what is possible with regular expressions.