In this chapter, you were introduced to regular expressions with a bit of history and their flavors. You learnt some use cases where regex are needed. Finally, we covered the basic rules and building blocks of writing regex, with a few examples. You also learnt the eager-matching behavior of the regex engine and how it may impact matching in alternations.

In the next chapter, we will go a level deeper and cover the core concepts of regex in detail, such as quantifiers, lazy vs greedy matching, anchors, negated character classes, Unicode and predefined character classes, special escape sequences, and the rules of escaping inside a character class.