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Regular Expression Backtracking Control Verb Reference

Feature	Syntax	Description	Example	JGsoft	Python	JavaScript	VBScript	XRegExp	.NET	Java	ICU	RE2	Perl	PCRE	PCRE2	PHP	Delphi	R	Ruby	std::regex	Boost	Tcl	POSIX	GNU	Oracle	XML	XPath
Control verb	`(FAIL)` or `(F)`	Fail to match, forcing the engine to backtrack, when reached during the normal matching process.	`a(*F)b\|c` matches `c` in `abc`	no	no	no	no	no	no	no	no	no	YES	7.4	YES	YES	YES	YES	no	no	ECMA 1.60	no	no	no	no	no	no
Control verb	`(*ACCEPT)`	Accept the match so far as the overall match when reached during the normal matching process.	`a(*ACCEPT)b\|c` matches `a`	no	no	no	no	no	no	no	no	no	YES	7.4	YES	YES	YES	YES	no	no	ECMA 1.60	no	no	no	no	no	no
Control verb	`(*ACCEPT)` inside a capturing group.	Accept the match so far of each parent capturing group in addition to accepting the overall match.	`a(b(*ACCEPT)c)d\|e` matches `ab`	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	YES	8.00	YES	YES	XE7	YES	n/a	n/a	ECMA 1.60	n/a	n/a	n/a	n/a	n/a	n/a
Control verb	`(*ACCEPT)`	Accept the match so far of the atomic group and continue matching the remainder of the regex when reached during the normal matching process.	`a(?>b(*ACCEPT)c).\|d` matches `abx`	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	n/a	YES	7.4–8.02	no	no	XE–XE6	no	n/a	n/a	ECMA 1.60	n/a	n/a	n/a	n/a	n/a	n/a
Control verb	`(*COMMIT)`	Commit to failure by stopping the matching process entirely when reached while backtracking.	`ab+(*COMMIT)d+\|.{3}` fails to match `abbbccc`	no	no	no	no	no	no	no	no	no	YES	7.4	YES	YES	YES	YES	no	no	ECMA 1.60	no	no	no	no	no	no
Control verb	`(*SKIP)`	Skip the match attempt by restarting the matching process at the position of `(*SKIP)` when reached while backtracking.	`ab+(*SKIP)d+\|.{3}` matches `ccc` in `abbbccc`	no	no	no	no	no	no	no	no	no	YES	7.4	YES	YES	YES	YES	no	no	ECMA 1.60	no	no	no	no	no	no
Control verb argument	`(:ARG)` and `(SKIP:ARG)`	Skip the match attempt by restarting the matching process at the position where `(:ARG)` was reached during the normal matching process before `(SKIP:ARG)` was reached while backtracking.	`a+(:ARG)b+(SKIP:ARG)d+\|.{3}` matches `bbb` in `aaabbbccc`	no	no	no	no	no	no	no	no	no	YES	8.10	YES	YES	XE7	YES	no	no	no	no	no	no	no	no	no
Control verb argument	`(MARK:ARG)` and `(SKIP:ARG)`	Skip the match attempt by restarting the matching process at the position where `(MARK:ARG)` was reached during the normal matching process before `(SKIP:ARG)` was reached while backtracking.	`a+(MARK:ARG)b+(SKIP:ARG)d+\|.{3}` matches `bbb` in `aaabbbccc`	no	no	no	no	no	no	no	no	no	YES	8.10	YES	YES	XE7	YES	no	no	no	no	no	no	no	no	no
Control verb	`(*PRUNE)`	Prune all backtracking positions when reached while backtracking, failing the match attempt but allowing the regex to advance one character and restart the matching process.	`ab+(*PRUNE)d+\|.{3}` matches `bbb` in `abbbccc`	no	no	no	no	no	no	no	no	no	YES	7.4	YES	YES	YES	YES	no	no	ECMA 1.60	no	no	no	no	no	no
Control verb	`(*THEN)`	If reached while backtracking then cancel the current alternative and continue with the next alternative.	`ab+(*THEN)d+\|.{3}` matches `abb` in `abbbccc`	no	no	no	no	no	no	no	no	no	YES	7.4	YES	YES	YES	YES	no	no	no	no	no	no	no	no	no
Control verb	`(*THEN)`	If reached while backtracking then cancel the innermost group that has alternative and continue with the remainder of the regex as if that group failed to match.	`a(b+(*THEN)d+\|.{2})\|a` matches `a` in `abbbccc`	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no	ECMA 1.60	no	no	no	no	no	no
Feature	Syntax	Description	Example	JGsoft	Python	JavaScript	VBScript	XRegExp	.NET	Java	ICU	RE2	Perl	PCRE	PCRE2	PHP	Delphi	R	Ruby	std::regex	Boost	Tcl	POSIX	GNU	Oracle	XML	XPath