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Replacement Strings Reference: Matched Text and Backreferences

Feature	Syntax	Description	Example	JGsoft	Python	JavaScript	VBScript	XRegExp	.NET	Java	ICU	RE2	Perl	PCRE2	PHP	Delphi	R	Ruby	std::regex	Boost	Tcl	Oracle	XPath
Ampersand	`\&`	Insert a literal ampersand.	Replacing with `\&` yields `&`	no	no	no	no	no	no	YES	YES	error	YES	extended	no	no	YES	no	sed	YES	YES	no	error
Whole match	`\&`	Insert the whole regex match.	Replacing `\d+` with `[\&]` in `1a2b` yields `[1]a[2]b`	YES	no	no	no	no	no	no	no	error	no	no	no	YES	no	YES	no	no	no	no	error
Whole match	`$&`	Insert the whole regex match.	Replacing `\d+` with `[$&]` in `1a2b` yields `[1]a[2]b`	YES	no	YES	YES	YES	YES	error	error	no	YES	10.45	no	YES	no	no	default	all default	no	no	error
Whole match	`&`	Insert the whole regex match.	Replacing `\d+` with `[&]` in `1a2b` yields `[1]a[2]b`	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no	sed	sed	YES	no	no
Whole match	`\0`	Insert the whole regex match.	Replacing `\d+` with `[\0]` in `1a2b` yields `[1]a[2]b`	YES	no	no	no	no	no	no	no	YES	no	no	YES	YES	no	YES	sed	sed	YES	no	error
Whole match	`$0`	Insert the whole regex match.	Replacing `\d+` with `[$0]` in `1a2b` yields `[1]a[2]b`	YES	no	no	no	YES	YES	YES	YES	no	error	YES	YES	YES	no	no	default VC’10–VC’13	all default	no	no	YES
Whole match	`${0}`	Insert the whole regex match.	Replacing `\d+` with `[${0}]` in `1a2b` yields `[1]a[2]b`	YES	no	no	no	YES	YES	error	error	no	error	YES	YES	YES	no	no	no	all default	no	no	error
Whole match	`\g<0>`	Insert the whole regex match.	Replacing `\d+` with `[\g<0>]` in `1a2b` yields `[1]a[2]b`	YES	YES	no	no	no	no	no	no	error	no	extended 10.45	no	no	no	no	no	no	no	no	error
Whole match	`$MATCH` and `${^MATCH}`	Insert the whole regex match.	Replacing `\d+` with `[$MATCH]` in `1a2b` yields `[1]a[2]b`	no	no	no	no	error	no	error	error	no	error	error	no	no	no	no	no	all default 1.42	no	no	error
Backreference	`\1` through `\9`	Insert the text matched by one of the first 9 capturing groups.	Replacing `(a)(b)(c)` with `\3\3\1` in `abc` yields `cca`	YES	YES	no	no	no	no	no	no	YES	YES	extended 10.45	YES	YES	YES	YES	sed	YES	YES	YES	error
Backreference	`\10` through `\99`	Insert the text matched by capturing groups 10 through 99.		YES	YES	no	no	no	no	no	no	no	no	extended 10.45	YES	YES	no	no	no	no	no	no	error
Backreference and literal	`\10` through `\99`	When there are fewer capturing groups than the 2-digit number, treat this as a single-digit backreference followed by a literal number instead of as an invalid backreference.	Replacing `(a)(b)(c)` with `\39\38\17` in `abc` yields `c9c8a7`	YES	no	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	no	no	YES	n/a	n/a	n/a	n/a	n/a	n/a	n/a
Backreference	`\100` through `\999`	Insert the text matched by capturing groups 100 through 999.		no	no	no	no	no	no	no	no	no	no	extended 10.45	no	no	no	no	no	no	no	no	error
Backreference and literal	`\100` through `\999`	When there are fewer capturing groups than the 3-digit number, treat this as a 2-digit backreference followed by a literal number instead of as an invalid backreference.	Replacing `(a)(b)(c)` with `\345\234\123` in `abc` yields `c45b34a23`	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	no	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a
Backreference	`$1` through `$9`	Insert the text matched by one of the first 9 capturing groups.	Replacing `(a)(b)(c)` with `$3$3$1` in `abc` yields `cca`	YES	no	YES	YES	YES	YES	YES	YES	no	YES	YES	YES	YES	no	no	default	all default	no	no	YES
Backreference	`$10` through `$99`	Insert the text matched by capturing groups 10 through 99.		YES	no	YES	YES	YES	YES	YES	YES	no	YES	YES	YES	YES	no	no	default	all default	no	no	YES
Backreference and literal	`$10` through `$99`	When there are fewer capturing groups than the 2-digit number, treat this as a single-digit backreference followed by a literal number instead of as an invalid backreference.	Replacing `(a)(b)(c)` with `$345$234$123` in `abc` yields `c45b34a23`	YES	n/a	YES	YES	no	ECMA	YES	YES	n/a	no	no	no	YES	n/a	n/a	no	no	n/a	n/a	YES
Backreference	`$100` through `$999`	Insert the text matched by capturing groups 100 through 999.		no	no	no	no	no	YES	YES	YES	no	YES	YES	no	no	no	no	no	all default 1.42	no	no	YES
Backreference and literal	`$100` through `$999`	When there are fewer capturing groups than the 3-digit number, treat this as a 2-digit backreference followed by a literal number instead of as an invalid backreference.	Replacing `(a)(b)(c)` with `$39$38$17` in `abc` yields `c9c8a7`	n/a	n/a	n/a	n/a	n/a	ECMA	YES	YES	n/a	no	no	n/a	n/a	n/a	n/a	n/a	no	n/a	n/a	YES
Backreference	`${1}` through `${999}`	Insert the text matched by capturing groups 1 through 999.	Replacing `(a)(b)(c)` with `${3}${3}${1}` in `abc` yields `cca`	YES	no	no	no	YES	YES	error	error	no	YES	YES	YES	YES	no	no	no	all default	no	no	error
Backreference	`\g<1>` through `\g<999>`	Insert the text matched by capturing groups 1 through 999.	Replacing `(a)(b)(c)` with `\g<3>\g<3>\g<1>` in `abc` yields `cca`	YES	YES	no	no	no	no	no	no	error	no	extended 10.45	no	no	no	no	no	no	no	no	error
Named backreference	`${name}`	Insert the text matched by the named capturing group “name”.	Replacing `(?'one'a)(?'two'b)` with `${two}${one}` in `ab` yields `ba`	YES	no	no	no	YES	YES	7 4 error	YES	no	error	YES	no	YES	no	no	no	no	no	no	error
Named backreference	`$+{name}`	Insert the text matched by the named capturing group “name”.	Replacing `(?'one'a)(?'two'b)` with `$+{two}$+{one}` in `ab` yields `ba`	no	no	no	no	error	no	error	error	no	YES	error	no	no	no	no	no	all default 1.42	no	no	error
Named backreference	`$name`	Insert the text matched by the named capturing group “name”.	Replacing `(?'one'a)(?'two'b)` with `$two$one` in `ab` yields `ba`	no	no	no	no	error	no	error	error	no	error	YES	no	no	no	no	no	no	no	no	error
Named backreference	`\g<name>`	Insert the text matched by the named capturing group “name”.	Replacing `(?P<one>a)(?P<two>b)` with `\g<two>\g<one>` in `ab` yields `ba`	YES	YES	no	no	no	no	no	no	error	no	extended 10.45	no	YES	no	no	no	no	no	no	error
Invalid backreference	Any supported backreference syntax	A backreference that indicates a number greater than the highest-numbered group or a name of a group that does not exist is replaced with the empty string.		V1 only	error	no	no	error	no	error	error	2017/05–2020/05	YES	error	YES	YES	YES	YES	default VC’10 sed VC’15	YES	YES	no	YES
Invalid backreference	Any supported backreference syntax	A backreference that indicates a number greater than the highest-numbered group or a name of a group that does not exist is treated as literal text that is inserted as such in the replacement.		V2 error	error	YES	YES	error	YES	error	error	no	no	error	no	no	no	no	sed VC’10–VC’13 error	no	no	YES	no
Invalid backreference	Any supported backreference syntax	No replacements are made at all if the replacement string contains a backreference that indicates a number greater than the highest-numbered group or a name of a group that does not exist.		V2 error	error	no	no	error	no	error	error	2020/06	no	error	no	no	no	no	sed VC’10–VC’13 error	no	no	no	no
Backreference to non-participating group	Any supported backreference syntax	A backreference to a non-participating capturing group is replaced with the empty string.		YES	3.5 2.4 error	YES	YES	YES	YES	YES	YES	YES	YES	error	YES	YES	YES	YES	YES	YES	YES	YES	YES
Last backreference	`\+`	Insert the text matched by the highest-numbered capturing group that actually participated in the match.	Replacing `(a)(z)?` with `[\+]` in `ab` yields `[a]b`	YES	no	no	no	no	no	no	no	error	no	no	no	YES	no	YES	no	no	no	no	error
Last backreference	`\+`	Insert the text matched by the highest-numbered capturing group, regardless of whether it participated in the match.	Replacing `(a)(z)?` with `[\+]` in `ab` yields `[]b`	no	no	no	no	no	no	no	no	error	no	no	no	no	no	no	no	no	no	no	error
Last backreference	`$+`	Insert the text matched by the highest-numbered capturing group that actually participated in the match.	Replacing `(a)(z)?` with `[$+]` in `ab` yields `[a]b`	YES	no	no	no	error	no	error	error	no	5.18	error	no	YES	no	no	no	no	no	no	error
Last backreference	`$+`	Insert the text matched by the highest-numbered capturing group, regardless of whether it participated in the match.	Replacing `(a)(z)?` with `[$+]` in `ab` yields `[]b`	no	no	no	YES	error	YES	error	error	no	5.14–5.16	error	no	no	no	no	no	all default 1.42	no	no	error
Last backreference	`$^N`	Insert the text matched by the highest-numbered capturing group that actually participated in the match.	Replacing `(a)(z)?` with `[$^N]` in `ab` yields `[a]b`	no	no	no	no	error	no	error	error	no	YES	error	no	no	no	no	no	all default 1.42	no	no	error
Last backreference	`$LAST_SUBMATCH_RESULT` and `${^LAST_SUBMATCH_RESULT}`	Insert the text matched by the highest-numbered capturing group that actually participated in the match.	Replacing `(a)(z)?` with `[$LAST_SUBMATCH_RESULT]` in `ab` yields `[a]b`	no	no	no	no	error	no	error	error	no	error	error	no	no	no	no	no	all default 1.42	no	no	error
Last backreference	`$LAST_PAREN_MATCH` and `${^LAST_PAREN_MATCH}`	Insert the text matched by the highest-numbered capturing group, regardless of whether it participated in the match.	Replacing `(a)(z)?` with `[$LAST_PAREN_MATCH]` in `ab` yields `[]b`	no	no	no	no	error	no	error	error	no	error	error	no	no	no	no	no	all default 1.42	no	no	error
Feature	Syntax	Description	Example	JGsoft	Python	JavaScript	VBScript	XRegExp	.NET	Java	ICU	RE2	Perl	PCRE2	PHP	Delphi	R	Ruby	std::regex	Boost	Tcl	Oracle	XPath