Backreferences

Introduction

Backreferences allow a regular expression to match repeated substrings by referring back to a previously captured group. They enable patterns to enforce consistency within the matched text.

Syntax

Backreferences use the following syntax:

• \1, \2, ...: Refers to a numbered capturing group in order of appearance and can only be used in replace and sub methods.
• \k<name>: Refers to a named capturing group and can be used within matching.

Example

(?<greeting>hello)\s+\k<greeting>

This matches hello followed by one or more space followed by hello again.