The following table lists the optional parameters for adding the backward reference modifier to the regular expression.
Rear reference configuration definition / Number backward reference. For example, (/ w) / 1 lookup two-write word characters. / k Name the backward reference. For example, (? / w) / k lookup two-write word characters. Expression (? <43> / w) / 43 performs the same operation. Single quotes can be used instead of angle brackets, such as / K'Char '.
Note the polymity between the octal escape code and the use of the / Number of the same representation. For more information on how the regular expression engine parsing polymity, see Reverse reference.
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Regular expression language elements
