Regular expressions are a formalism used to describe regular languages and form the basis of several pattern-matching libraries. However, many interesting patterns either are difficult to describe or cannot be described by pure regular expressions. Because of these limitations, modern scripting languages have pattern matching libraries based on regexes, ie, extensions of regular expressions mainly composed by a set of ad-hoc constructions that focus on specific problems. Although very useful in practice, these implementations are complex and distant from the original formalism of regular expressions. Parsing Expression Grammars (PEG) are a formal alternative to recognize patterns and it is much more expressive than pure regular expressions and does not need use ad-hoc constructions. The goal of this work is to study the convertion of regexes to PEGs. To accomplish this task, we studied the current implementations of regexes and show how to convert some constructions to PEGs. Finally, we present an implementation that convert regexes to PEGs for the Lua language.