Groups and Backreferences in Regular Expressions

1. Capturing Groups

Capturing groups are used to treat multiple characters as a single unit. They are created by placing the characters to be grouped inside a set of parentheses (). This allows you to apply quantifiers to the entire group and later refer to the matched substring.

2. Non-Capturing Groups

Non-capturing groups are used to group multiple characters without capturing them for later use. They are created by placing the characters to be grouped inside a set of parentheses with a ?: prefix. This is useful when you want to apply a quantifier to a group but don't need to refer to it later.

3. Named Capturing Groups

Named capturing groups allow you to assign a name to a capturing group. This makes it easier to refer to the matched substring later. They are created by placing the characters to be grouped inside a set of parentheses with a ?<name> prefix.

4. Backreferences

Backreferences allow you to refer to a previously matched capturing group within the same regular expression. They are created using the backslash \ followed by the number of the capturing group. For named capturing groups, you can use \k<name>.

5. Conditional Groups

Conditional groups allow you to specify different patterns based on whether a previous capturing group matched or not. They are created using the syntax (?(condition)true-pattern|false-pattern). This is useful for creating more complex and flexible patterns.