Replacement Reference

Replacement Strings Reference: Context and Case Conversion

Feature	Syntax	Description	Example	JGsoft	.NET	Java	Perl	PCRE2	PHP	Delphi	R	JavaScript	VBScript	XRegExp	Python	Ruby	std::regex	Boost	Tcl ARE	Oracle	XPath
Match Context	\` (backslash backtick)	Insert the part of the subject string to the left of the regex match	Replacing `b` with \` in `abc` yields `aac`	YES	no	no	no	no	no	YES	no	no	no	no	no	YES	no	no	no	no	error
Match Context	$` (dollar backtick)	Insert the part of the subject string to the left of the regex match	Replacing `b` with $` in `abc` yields `aac`	YES	YES	error	YES	error	no	YES	no	YES	YES	YES	no	no	default	all default	no	no	error
Match Context	`$PREMATCH` and `${^PREMATCH}`	Insert the part of the subject string to the left of the regex match	Replacing `b` with `$PREMATCH` in `abc` yields `aac`	no	no	error	error	error	no	no	no	no	no	error	no	no	no	all default 1.42–1.85	no	no	error
Match Context	`\'` (backslash quote)	Insert the part of the subject string to the right of the regex match	Replacing `b` with `\'` in `abc` yields `acc`	YES	no	no	no	no	no	YES	no	no	no	no	no	YES	no	no	no	no	error
Match Context	`$'` (dollar quote)	Insert the part of the subject string to the right of the regex match	Replacing `b` with `$'` in `abc` yields `acc`	YES	YES	error	YES	error	no	YES	no	YES	YES	YES	no	no	default	all default	no	no	error
Match Context	`$POSTMATCH` and `${^POSTMATCH}`	Insert the part of the subject string to the right of the regex match	Replacing `b` with `$POSTMATCH` in `abc` yields `acc`	no	no	error	error	error	no	no	no	no	no	error	no	no	no	all default 1.42–1.85	no	no	error
Match Context	`\_`	Insert the whole subject string	Replacing `b` with `\_` in `abc` yields `aabcc`	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no	error
Match Context	`$_`	Insert the whole subject string	Replacing `b` with `$_` in `abc` yields `aabcc`	YES	YES	error	error	error	no	YES	no	no	YES	error	no	no	no	no	no	no	error
Case Conversion	`\U0` and `\U1` through `\U99`	Insert the whole regex match or the 1st through 99th backreference with all letters in the matched text converted to uppercase.	Replacing `.+` with `\U0` in `HeLlO WoRlD` yields `HELLO WORLD`	YES	no	no	no	no	no	YES	no	no	no	no	3.7–3.10 error	no	no	no	no	no	error
Case Conversion	`\L0` and `\L1` through `\L99`	Insert the whole regex match or the 1st through 99th backreference with all letters in the matched text converted to lowercase.	Replacing `.+` with `\L0` in `HeLlO WoRlD` yields `hello world`	YES	no	no	no	no	no	YES	no	no	no	no	3.7–3.10 error	no	no	no	no	no	error
Case Conversion	`\F0` and `\F1` through `\F99`	Insert the whole regex match or the 1st through 99th backreference with the first letter in the matched text converted to uppercase and the remaining letters converted to lowercase.	Replacing `.+` with `\F0` in `HeLlO WoRlD` yields `Hello world`	YES	no	no	no	extended error	no	YES	no	no	no	no	3.7–3.10 error	no	no	no	no	no	error
Case Conversion	`\I0` and `\I1` through `\I99`	Insert the whole regex match or the 1st through 99th backreference with the first letter of each word in the matched text converted to uppercase and the remaining letters converted to lowercase.	Replacing `.+` with `\I0` in `HeLlO WoRlD` yields `Hello World`	YES	no	no	no	extended error	no	YES	no	no	no	no	3.7–3.10 error	no	no	no	no	no	error
Case Conversion	`\U`	All literal text and all text inserted by replacement text tokens after `\U` up to the next `\E` or `\L` is converted to uppercase.	Replacing `(\w+) (\w+)` with `\U$1 CrUeL \E$2` in `HeLlO WoRlD` yields `HELLO CRUEL WoRlD`	no	no	no	YES	extended	no	no	no	no	no	no	3.7–3.10 error	no	no	all default	no	no	error
Case Conversion	`\L`	All literal text and all text inserted by replacement text tokens after `\L` up to the next `\E` or `\U` is converted to lowercase.	Replacing `(\w+) (\w+)` with `\L$1 CrUeL \E$2` in `HeLlO WoRlD` yields `hello cruel WoRlD`	no	no	no	YES	extended	no	no	no	no	no	no	3.7–3.10 error	no	no	all default	no	no	error
Case Conversion	`\u`	The first character after `\u` that is inserted into the replacement text as a literal or by a token is converted to uppercase.	Replacing `(\w+) (\w+)` with `\u$1 \ucRuEl \u$2` in `hElLo wOrLd` yields `HElLO CRuEl WOrLd`	no	no	no	YES	extended	no	no	no	no	no	no	3.7–3.10 error	no	no	all default	no	no	error
Case Conversion	`\l`	The first character after `\l` that is inserted into the replacement text as a literal or by a token is converted to lowercase.	Replacing `(\w+) (\w+)` with `\l$1 \lCrUeL \l$2` in `HeLlO WoRlD` yields `heLlO crUeL woRlD`	no	no	no	YES	extended	no	no	no	no	no	no	3.7–3.10 error	no	no	all default	no	no	error
Case Conversion	`\u\L`	The first character after `\u\L` that is inserted into the replacement text as a literal or by a token is converted to uppercase and the following characters up to the next `\E` or `\U` are converted to lowercase.	Replacing `(\w+) (\w+)` with `\u\L$1 \uCrUeL \E\u$2` in `HeLlO wOrLd` yields `Hello Cruel WOrLd`	no	no	no	YES	no	no	no	no	no	no	no	3.7–3.10 error	no	no	no	no	no	error
Case Conversion	`\l\U`	The first character after `\l\U` that is inserted into the replacement text as a literal or by a token is converted to lowercase and the following characters up to the next `\E` or `\L` are converted to uppercase.	Replacing `(\w+) (\w+)` with `\l\U$1 \lCrUeL \E\l$2` in `HeLlO WoRlD` yields `hELLO cRUEL woRlD`	no	no	no	YES	no	no	no	no	no	no	no	3.7–3.10 error	no	no	no	no	no	error
Case Conversion	`\L\u`	The first character after `\L\u` that is inserted into the replacement text as a literal or by a token is converted to uppercase and the following characters up to the next `\E` or `\U` are converted to lowercase.	Replacing `(\w+) (\w+)` with `\L\u$1 \uCrUeL \E\u$2` in `HeLlO wOrLd` yields `Hello Cruel WOrLd`	no	no	no	no	no	no	no	no	no	no	no	3.7–3.10 error	no	no	all default	no	no	error
Case Conversion	`\U\l`	The first character after `\U\l` that is inserted into the replacement text as a literal or by a token is converted to lowercase and the following characters up to the next `\E` or `\L` are converted to uppercase.	Replacing `(\w+) (\w+)` with `\U\l$1 \lCrUeL \E\l$2` in `HeLlO WoRlD` yields `hELLO cRUEL woRlD`	no	no	no	no	no	no	no	no	no	no	no	3.7–3.10 error	no	no	all default	no	no	error
Feature	Syntax	Description	Example	JGsoft	.NET	Java	Perl	PCRE2	PHP	Delphi	R	JavaScript	VBScript	XRegExp	Python	Ruby	std::regex	Boost	Tcl ARE	Oracle	XPath