Note
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The following table lists optional parameters that add backreference modifiers to a regular expression.
| Backreference construct | Definition |
|---|---|
| \number | Backreference. For example, (\w)\1 finds doubled word characters. |
| \k<name> | Named backreference. For example, (?<char>\w)\k<char> finds doubled word characters. The expression (?<43>\w)\43 does the same. You can use single quotes instead of angle brackets; for example, \k'char'. |
Note the ambiguity between octal escape codes and \number backreferences that use the same notation. See Backreferences for details on how the regular expression engine resolves the ambiguity.