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if pattern contains parenthesized substrings, replacement may contain substrings of the form\\ digit, which will be replaced by the text matching the digit'th parenthesized substring; \\0 will produce the entire contents of string. up to nine substrings may be used. parentheses may be nested, in which case they are counted by the opening parenthesis.
one thing to take note of is that if you use an integer value as the replacement one thing to take note of is that if you use an integer value as the replacement parameter, you may not get the results you expect.
