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Replacement Strings Reference: Context

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
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	no	no	error	no	no	no	YES	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 $` in `abc` yields `aac`	YES	no	YES	YES	YES	YES	error	error	no	YES	10.45	no	YES	no	no	default	all default	no	no	error
Match Context	`$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	no	no	error	no	error	error	no	error	error	no	no	no	no	no	all default 1.42	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	no	no	error	no	no	no	YES	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	no	YES	YES	YES	YES	error	error	no	YES	10.45	no	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 `$POSTMATCH` in `abc` yields `acc`	no	no	no	no	error	no	error	error	no	error	error	no	no	no	no	no	all default 1.42	no	no	error
Match Context	`$_`	Insert the whole subject string	Replacing `b` with `$_` in `abc` yields `aabcc`	YES	no	no	YES	error	YES	error	error	no	error	10.45	no	YES	no	no	no	no	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