| Feature | Syntax | Description | Example | .NET | Java | Perl | PCRE2 | PHP | Delphi | R | JavaScript | VBScript | XRegExp | Python | Ruby | std::regex | Boost | Tcl ARE | Oracle | XPath |
|---|
| Ampersand |
\& |
Insert a literal ampersand. |
Replacing with \& yields & |
no | YES | YES | extended | no | no | YES | no | no | no | no | no | sed | YES | YES | no | error |
| Whole match |
\& |
Insert the whole regex match. |
Replacing \d+ with [\&] in 1a2b yields [1]a[2]b |
no | no | no | no | no | YES | no | no | no | no | 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 | error | YES | error | no | YES | no | YES | YES | 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 | sed | sed | YES | no | no |
| Whole match |
\0 |
Insert the whole regex match. |
Replacing \d+ with [\0] in 1a2b yields [1]a[2]b |
no | no | no | no | YES | YES | no | no | no | no | 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 | YES | error | YES | YES | YES | no | no | no | YES | no | no | default
VC’08–VC’13 | all
default | no | no | YES |
| Whole match |
\g<0> |
Insert the whole regex match. |
Replacing \d+ with [\g<0>] in 1a2b yields [1]a[2]b |
no | no | no | no | no | no | no | no | no | no | YES | 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 | error | error | error | no | no | no | no | no | error | no | no | no | all
default
1.42–1.83 | 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 |
no | no | YES | no | YES | YES | YES | no | no | no | YES | YES | sed | YES | YES | YES | error |
| Backreference |
\10 through \99 |
Insert the text matched by capturing groups 10 through 99. |
|
no | no | no | no | YES | YES | no | no | no | no | YES | no | no | no | no | no | no |
| 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 |
n/a | n/a | n/a | n/a | no | YES | n/a | n/a | n/a | n/a | no | 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 | YES | YES | YES | YES | YES | no | 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 | YES | YES | YES | YES | YES | no | 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 $39$38$17 in abc yields c9c8a7 |
ECMA | YES | no | no | no | YES | n/a | YES | YES | no | n/a | n/a | no | no | n/a | n/a | YES |
| Backreference |
${1} through ${99} |
Insert the text matched by capturing groups 1 through 99. |
Replacing (a)(b)(c) with ${3}${3}${1} in abc yields cca |
YES | error | YES | YES | YES | YES | no | no | no | YES | no | no | no | all
default | no | no | error |
| Backreference |
\g<1> through \g<99> |
Insert the text matched by capturing groups 1 through 99. |
Replacing (a)(b)(c) with \g<3>\g<3>\g<1> in abc yields cca |
no | no | no | no | no | no | no | no | no | no | YES | 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 | 7 | error | YES | no | YES | no | no | 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 | error | 5.10 | error | no | no | no | no | no | error | no | no | no | all
default
1.42–1.83 | 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 | error | error | YES | no | no | no | no | no | error | 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 |
no | no | no | no | no | YES | no | no | no | no | YES | 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. |
|
no | error | YES | error | YES | YES | YES | no | no | error | error | YES | default VC’08–VC’22
sed VC’15–VC’22 | YES | YES | YES | 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. |
|
YES | error | no | error | no | no | no | YES | YES | error | error | no | sed
VC’08–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 | YES | YES | error | YES | YES | YES | YES | YES | YES | 3.5 | 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 |
no | no | no | no | no | YES | no | no | no | no | 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 | 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 |
no | error | 5.18 | error | no | YES | no | no | no | error | 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 |
YES | error | 5.8–5.16 | error | no | no | no | no | YES | error | no | no | no | all
default
1.42–1.83 | 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 | error | YES | error | no | no | no | no | no | error | no | no | no | all
default
1.42–1.83 | 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 | error | error | error | no | no | no | no | no | error | no | no | no | all
default
1.42–1.83 | 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 | error | error | error | no | no | no | no | no | error | no | no | no | all
default
1.42–1.83 | no | no | error |
| Feature | Syntax | Description | Example | .NET | Java | Perl | PCRE2 | PHP | Delphi | R | JavaScript | VBScript | XRegExp | Python | Ruby | std::regex | Boost | Tcl ARE | Oracle | XPath |
|---|
