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Substitutions are allowed only within replacement patterns. For similar functionality within regular expressions, use a backreference (for example, \1). For details on backreferences, see Backreferences and Backreference Constructs.

Character escapes and substitutions are the only special constructs recognized in a replacement pattern. All the syntactic constructs described in the following sections are allowed only in regular expressions; they are not recognized in replacement patterns. For example, the replacement pattern a*${txt}b inserts the string "a*" followed by the substring matched by the txt capturing group, if any, followed by the string "b". The * character is not recognized as a metacharacter within a replacement pattern. Similarly, $ patterns are not recognized within regular expression matching patterns. Within regular expressions, $ designates the end of the string.

The following table shows how to define named and numbered replacement patterns.

Character Description


Substitutes the last substring matched by group number number (decimal).


Substitutes the last substring matched by a (?<name> ) group.


Substitutes a single "$" literal.


Substitutes a copy of the entire match itself.


Substitutes all the text of the input string before the match.


Substitutes all the text of the input string after the match.


Substitutes the last group captured.


Substitutes the entire input string.