Regular expression (English Wikipedia)

Cezar Câmpeanu; Kai Salomaa & Sheng Yu (Dec 2003). "A Formal Study of Practical Regular Expressions". International Journal of Foundations of Computer Science. 14 (6): 1007–1018. doi:10.1142/S012905410300214X. Archived from the original on 2015-07-04. Retrieved 2015-07-03. Theorem 3 (p.9)

archive-it.org (Global: 1,292^nd place; English: 869^th place)

wayback.archive-it.org

Ritchie, D. M.; Thompson, K. L. (June 1970). QED Text Editor (PDF). MM-70-1373-3. Archived from the original (PDF) on 2015-02-03. Retrieved 2022-09-05. Reprinted as "QED Text Editor Reference Manual", MHCC-004, Murray Hill Computing, Bell Laboratories (October 1972).

archive.org (Global: 6^th place; English: 6^th place)

Sipser (1998) Sipser, Michael (1998). "Chapter 1: Regular Languages". Introduction to the Theory of Computation. PWS Publishing. pp. 31–90. ISBN 978-0-534-94728-6.

arxiv.org (Global: 49^th place; English: 31^st place)

Gelade & Neven (2008, p. 332, Thm.4.1) Gelade, Wouter; Neven, Frank (2008). Succinctness of the Complement and Intersection of Regular Expressions. Proceedings of the 25th International Symposium on Theoretical Aspects of Computer Science (STACS 2008). pp. 325–336. arXiv:0802.2869. Archived from the original on 2011-07-18. Retrieved 2009-06-15.
Based on Gelade & Neven (2008), a regular expression of length about 850 such that its complement has a length about 2³² can be found at File:RegexComplementBlowup.png. Gelade, Wouter; Neven, Frank (2008). Succinctness of the Complement and Intersection of Regular Expressions. Proceedings of the 25th International Symposium on Theoretical Aspects of Computer Science (STACS 2008). pp. 325–336. arXiv:0802.2869. Archived from the original on 2011-07-18. Retrieved 2009-06-15.
Kearns, Steven (August 2013). "Sublinear Matching With Finite Automata Using Reverse Suffix Scanning". arXiv:1308.3822 [cs.DS].
Schmid, Markus L. (March 2019). "Regular Expressions with Backreferences: Polynomial-Time Matching Techniques". arXiv:1903.05896 [cs.FL].

bell-labs.com (Global: low place; English: low place)

cm.bell-labs.com

Ritchie, Dennis M. "An incomplete history of the QED Text Editor". Archived from the original on 1999-02-21. Retrieved 9 October 2013.
Ritchie, D. M.; Thompson, K. L. (June 1970). QED Text Editor (PDF). MM-70-1373-3. Archived from the original (PDF) on 2015-02-03. Retrieved 2022-09-05. Reprinted as "QED Text Editor Reference Manual", MHCC-004, Murray Hill Computing, Bell Laboratories (October 1972).

bkase.github.io (Global: low place; English: low place)

"CUDA grep". bkase.github.io. Archived from the original on 2020-10-07. Retrieved 2019-10-22.

books.google.com (Global: 3^rd place; English: 3^rd place)

Mitkov, Ruslan (2003). The Oxford Handbook of Computational Linguistics. Oxford University Press. p. 754. ISBN 978-0-19-927634-9. Archived from the original on 2017-02-28. Retrieved 2016-07-25.
Lawson, Mark V. (17 September 2003). Finite Automata. CRC Press. pp. 98–100. ISBN 978-1-58488-255-8. Archived from the original on 27 February 2017. Retrieved 25 July 2016.

boskent.com (Global: low place; English: low place)

s3.boskent.com

"Regular expressions for deciding divisibility". s3.boskent.com. Retrieved 2024-02-21.

catb.org (Global: 7,578^th place; English: 6,551^st place)

Raymond, Eric S. citing Dennis Ritchie (2003). "Jargon File 4.4.7: grep". Archived from the original on 2011-06-05. Retrieved 2009-02-17.

dagstuhl.de (Global: low place; English: low place)

drops.dagstuhl.de

Gelade & Neven (2008, p. 332, Thm.4.1) Gelade, Wouter; Neven, Frank (2008). Succinctness of the Complement and Intersection of Regular Expressions. Proceedings of the 25th International Symposium on Theoretical Aspects of Computer Science (STACS 2008). pp. 325–336. arXiv:0802.2869. Archived from the original on 2011-07-18. Retrieved 2009-06-15.
Based on Gelade & Neven (2008), a regular expression of length about 850 such that its complement has a length about 2³² can be found at File:RegexComplementBlowup.png. Gelade, Wouter; Neven, Frank (2008). Succinctness of the Complement and Intersection of Regular Expressions. Proceedings of the 25th International Symposium on Theoretical Aspects of Computer Science (STACS 2008). pp. 325–336. arXiv:0802.2869. Archived from the original on 2011-07-18. Retrieved 2009-06-15.

doi.org (Global: 2^nd place; English: 2^nd place)

Thompson 1968. Thompson, Ken (1968). "Programming Techniques: Regular expression search algorithm". Communications of the ACM. 11 (6): 419–422. doi:10.1145/363347.363387. S2CID 21260384.
Johnson et al. 1968. Johnson, Walter L.; Porter, James H.; Ackley, Stephanie I.; Ross, Douglas T. (1968). "Automatic generation of efficient lexical processors using finite state techniques". Communications of the ACM. 11 (12): 805–813. doi:10.1145/364175.364185. S2CID 17253809.
Aycock 2003, p. 98. Aycock, John (June 2003). "A brief history of just-in-time" (PDF). ACM Computing Surveys. 35 (2): 97–113. doi:10.1145/857076.857077. S2CID 15345671.
Gruber & Holzer (2008) Gruber, Hermann; Holzer, Markus (2008). Finite Automata, Digraph Connectivity, and Regular Expression Size (PDF). Proceedings of the 35th International Colloquium on Automata, Languages and Programming (ICALP 2008). Lecture Notes in Computer Science. Vol. 5126. pp. 39–50. doi:10.1007/978-3-540-70583-3_4. ISBN 978-3-540-70582-6. Archived (PDF) from the original on 2011-07-11. Retrieved 2011-02-03.
Kozen (1991)^{[page needed]} Kozen, Dexter (1991). "A completeness theorem for Kleene algebras and the algebra of regular events". [1991] Proceedings Sixth Annual IEEE Symposium on Logic in Computer Science. pp. 214–225. doi:10.1109/LICS.1991.151646. hdl:1813/6963. ISBN 978-0-8186-2230-4. S2CID 19875225.
Bormann, Carsten; Bray, Tim. I-Regexp: An Interoperable Regular Expression Format. Internet Engineering Task Force. doi:10.17487/RFC9485. RFC 9485. Retrieved 11 March 2024.
Cezar Câmpeanu; Kai Salomaa & Sheng Yu (Dec 2003). "A Formal Study of Practical Regular Expressions". International Journal of Foundations of Computer Science. 14 (6): 1007–1018. doi:10.1142/S012905410300214X. Archived from the original on 2015-07-04. Retrieved 2015-07-03. Theorem 3 (p.9)
Navarro, Gonzalo (10 November 2001). "NR-grep: a fast and flexible pattern-matching tool" (PDF). Software: Practice and Experience. 31 (13): 1265–1312. doi:10.1002/spe.411. S2CID 3175806. Archived (PDF) from the original on 7 October 2020. Retrieved 21 November 2019.

github.com (Global: 380^th place; English: 337^th place)

SRE: Atomic Grouping (?>...) is not supported #34627
Wall, Larry (1994-10-18). "Perl 5: perlre.pod". GitHub.
Zakharevich, Ilya (1997-11-19). "Jumbo Regexp Patch Applied (with Minor Fix-Up Tweaks): Perl/perl5@c277df4". GitHub.
"travisdowns/polyregex". GitHub. 5 July 2019. Archived from the original on 14 September 2020. Retrieved 21 November 2019.

gnu.org (Global: 1,901^st place; English: 1,743^rd place)

git.savannah.gnu.org

"gnulib/lib/dfa.c". Archived from the original on 2021-08-18. Retrieved 2022-02-12. If the scanner detects a transition on backref, it returns a kind of "semi-success" indicating that the match will have to be verified with a backtracking matcher.

googleblog.blogspot.com (Global: 6,935^th place; English: 8,461^st place)

Horowitz, Bradley (24 October 2011). "A fall sweep". Google Blog. Archived from the original on 21 October 2018. Retrieved 4 May 2019.

grovf.com (Global: low place; English: low place)

"GRegex – Faster Analytics for Unstructured Text Data". grovf.com. Archived from the original on 2020-10-07. Retrieved 2026-04-20.

hdl.handle.net (Global: 66^th place; English: 34^th place)

Kozen (1991)^{[page needed]} Kozen, Dexter (1991). "A completeness theorem for Kleene algebras and the algebra of regular events". [1991] Proceedings Sixth Annual IEEE Symposium on Logic in Computer Science. pp. 214–225. doi:10.1109/LICS.1991.151646. hdl:1813/6963. ISBN 978-0-8186-2230-4. S2CID 19875225.

hermann-gruber.com (Global: low place; English: low place)

Gruber & Holzer (2008) Gruber, Hermann; Holzer, Markus (2008). Finite Automata, Digraph Connectivity, and Regular Expression Size (PDF). Proceedings of the 35th International Colloquium on Automata, Languages and Programming (ICALP 2008). Lecture Notes in Computer Science. Vol. 5126. pp. 39–50. doi:10.1007/978-3-540-70583-3_4. ISBN 978-3-540-70582-6. Archived (PDF) from the original on 2011-07-11. Retrieved 2011-02-03.

howtogeek.com (Global: 8,729^th place; English: 6,329^th place)

Heddings, Anthony (11 March 2020). "How Do You Actually Use Regex?". howtogeek.com. Retrieved 24 February 2024.

ietf.org (Global: 731^st place; English: 625^th place)

datatracker.ietf.org

Bormann, Carsten; Bray, Tim. I-Regexp: An Interoperable Regular Expression Format. Internet Engineering Task Force. doi:10.17487/RFC9485. RFC 9485. Retrieved 11 March 2024.

imath.kiev.ua (Global: low place; English: low place)

umj.imath.kiev.ua

Redko, V.N. (1964). "On defining relations for the algebra of regular events". Ukrainskii Matematicheskii Zhurnal (in Russian). 16 (1): 120–126. Archived from the original on 2018-03-29. Retrieved 2018-03-28.

laurikari.net (Global: low place; English: low place)

Laurikari (2009) Laurikari, Ville (2009). "TRE library 0.7.6". Archived from the original on 2010-07-14. Retrieved 2009-04-01.

man7.org (Global: low place; English: low place)

Kerrisk, Michael. "grep(1) - Linux manual page". man7.org. Retrieved 31 January 2023.

nmsu.edu (Global: 9,083^rd place; English: 6,016^th place)

cs.nmsu.edu

Leung, Hing (16 September 2010). "Regular Languages and Finite Automata" (PDF). New Mexico State University. Archived from the original (PDF) on 5 December 2013. Retrieved 13 August 2019. The concept of regular events was introduced by Kleene via the definition of regular expressions.

opengroup.org (Global: 6,630^th place; English: 5,295^th place)

pubs.opengroup.org

"9.3.6 BREs Matching Multiple Characters". The Open Group Base Specifications Issue 7, 2018 edition. The Open Group. 2017. Retrieved December 10, 2023.

oracle.com (Global: 2,532^nd place; English: 1,847^th place)

docs.oracle.com

"Essential classes: Regular Expressions: Quantifiers: Differences Among Greedy, Reluctant, and Possessive Quantifiers". The Java Tutorials. Oracle. Archived from the original on 7 October 2020. Retrieved 23 December 2016.

pcre.org (Global: low place; English: low place)

"PCRE - Perl Compatible Regular Expressions". www.pcre.org. Retrieved 2024-04-07.

perl.org (Global: low place; English: low place)

perldoc.perl.org

Wall, Larry (2006). "Perl Regular Expressions". perlre. Archived from the original on 2009-12-31. Retrieved 2006-10-10.
"Perl Regular Expression Documentation". perldoc.perl.org. Archived from the original on December 31, 2009. Retrieved November 5, 2024.
The character 'm' is not always required to specify a Perl match operation. For example, m/[^abc]/ could also be rendered as /[^abc]/. The 'm' is only necessary if the user wishes to specify a match operation without using a forward-slash as the regex delimiter. Sometimes it is useful to specify an alternate regex delimiter in order to avoid "delimiter collision". See 'perldoc perlre Archived 2009-12-31 at the Wayback Machine' for more details.

dev.perl.org

Wall (2002) Wall, Larry (2002). "Apocalypse 5: Pattern Matching". Archived from the original on 2010-01-12. Retrieved 2006-10-11.

plover.com (Global: low place; English: low place)

perl.plover.com

"Perl Regular Expression Matching is NP-Hard". perl.plover.com. Archived from the original on 2020-10-07. Retrieved 2019-11-21.

postgresql.org (Global: low place; English: low place)

"Documentation: 9.3: Pattern Matching". PostgreSQL. Archived from the original on 2020-10-07. Retrieved 2013-10-12.

princeton.edu (Global: 802^nd place; English: 528^th place)

cs.princeton.edu

Kernighan, Brian (2007-08-08). "A Regular Expressions Matcher". Beautiful Code. O'Reilly Media. pp. 1–2. ISBN 978-0-596-51004-6. Archived from the original on 2020-10-07. Retrieved 2013-05-15.

python.org (Global: 4,399^th place; English: 3,941^st place)

docs.python.org

"Regular Expression Syntax". Python 3.5.0 documentation. Python Software Foundation. Archived from the original on 18 July 2018. Retrieved 10 October 2015.

rand.org (Global: 3,236^th place; English: 2,152^nd place)

Kleene 1951. Kleene, Stephen C. (1951). "Representation of Events in Nerve Nets and Finite Automata". In Shannon, Claude E.; McCarthy, John (eds.). Automata Studies (PDF). Princeton University Press. pp. 3–42. Archived (PDF) from the original on 2020-10-07. Retrieved 2017-12-10.
Kleene 1951, pg46

regular-expressions.info (Global: low place; English: low place)

Goyvaerts, Jan. "Regular Expression Tutorial - Learn How to Use Regular Expressions". Regular-Expressions.info. Archived from the original on 2016-11-01. Retrieved 2016-10-31.
"How a Regex Engine Works Internally". regular-expressions.info. Retrieved 24 February 2024.
"Atomic Grouping". Regex Tutorial. Archived from the original on 7 October 2020. Retrieved 24 November 2019.

rfc-editor.org (Global: 747^th place; English: 325^th place)

Bormann, Carsten; Bray, Tim. I-Regexp: An Interoperable Regular Expression Format. Internet Engineering Task Force. doi:10.17487/RFC9485. RFC 9485. Retrieved 11 March 2024.

scribd.com (Global: 467^th place; English: 428^th place)

Conway, Damian (2005). "Regular Expressions, End of String". Perl Best Practices. O'Reilly. p. 240. ISBN 978-0-596-00173-5. Archived from the original on 2020-10-07. Retrieved 2017-09-10.

semanticscholar.org (Global: 15^th place; English: 8^th place)

api.semanticscholar.org

Thompson 1968. Thompson, Ken (1968). "Programming Techniques: Regular expression search algorithm". Communications of the ACM. 11 (6): 419–422. doi:10.1145/363347.363387. S2CID 21260384.
Johnson et al. 1968. Johnson, Walter L.; Porter, James H.; Ackley, Stephanie I.; Ross, Douglas T. (1968). "Automatic generation of efficient lexical processors using finite state techniques". Communications of the ACM. 11 (12): 805–813. doi:10.1145/364175.364185. S2CID 17253809.
Aycock 2003, p. 98. Aycock, John (June 2003). "A brief history of just-in-time" (PDF). ACM Computing Surveys. 35 (2): 97–113. doi:10.1145/857076.857077. S2CID 15345671.
Kozen (1991)^{[page needed]} Kozen, Dexter (1991). "A completeness theorem for Kleene algebras and the algebra of regular events". [1991] Proceedings Sixth Annual IEEE Symposium on Logic in Computer Science. pp. 214–225. doi:10.1109/LICS.1991.151646. hdl:1813/6963. ISBN 978-0-8186-2230-4. S2CID 19875225.
Navarro, Gonzalo (10 November 2001). "NR-grep: a fast and flexible pattern-matching tool" (PDF). Software: Practice and Experience. 31 (13): 1265–1312. doi:10.1002/spe.411. S2CID 3175806. Archived (PDF) from the original on 7 October 2020. Retrieved 21 November 2019.

sourceforge.net (Global: 1,842^nd place; English: 1,520^th place)

vimdoc.sourceforge.net

"Vim documentation: pattern". Vimdoc.sourceforge.net. Archived from the original on 2020-10-07. Retrieved 2013-09-25.

stackexchange.com (Global: 4,114^th place; English: 3,027^th place)

cs.stackexchange.com

Wandering Logic. "How to simulate lookaheads and lookbehinds in finite state automata?". Computer Science Stack Exchange. Archived from the original on 7 October 2020. Retrieved 24 November 2019.

stanford.edu (Global: 194^th place; English: 182^nd place)

infolab.stanford.edu

Aho & Ullman 1992, 10.11 Bibliographic Notes for Chapter 10, p. 589. Aho, Alfred V.; Ullman, Jeffrey D. (1992). "Chapter 10. Patterns, Automata, and Regular Expressions" (PDF). Foundations of Computer Science. Archived from the original on 2020-10-07. Retrieved 2013-12-14.

swtch.com (Global: low place; English: low place)

Russ Cox (2009). "Regular Expression Matching: the Virtual Machine Approach". swtch.com. Digression: POSIX Submatching
Cox (2007) Cox, Russ (2007). "Regular Expression Matching Can Be Simple and Fast". Archived from the original on 2010-01-01. Retrieved 2008-04-27.

tcl.tk (Global: low place; English: low place)

"New Regular Expression Features in Tcl 8.1". Archived from the original on 2020-10-07. Retrieved 2013-10-11.

tufts.edu (Global: 192^nd place; English: 165^th place)

cs.tufts.edu

Aycock 2003, p. 98. Aycock, John (June 2003). "A brief history of just-in-time" (PDF). ACM Computing Surveys. 35 (2): 97–113. doi:10.1145/857076.857077. S2CID 15345671.

uchile.cl (Global: 2,618^th place; English: 4,466^th place)

users.dcc.uchile.cl

Navarro, Gonzalo (10 November 2001). "NR-grep: a fast and flexible pattern-matching tool" (PDF). Software: Practice and Experience. 31 (13): 1265–1312. doi:10.1002/spe.411. S2CID 3175806. Archived (PDF) from the original on 7 October 2020. Retrieved 21 November 2019.

unicode.org (Global: 691^st place; English: 581^st place)

"UTS#18 on Unicode Regular Expressions, Annex A: Character Blocks". Archived from the original on 2020-10-07. Retrieved 2010-02-05.

web.archive.org (Global: 1^st place; English: 1^st place)

Goyvaerts, Jan. "Regular Expression Tutorial - Learn How to Use Regular Expressions". Regular-Expressions.info. Archived from the original on 2016-11-01. Retrieved 2016-10-31.
Mitkov, Ruslan (2003). The Oxford Handbook of Computational Linguistics. Oxford University Press. p. 754. ISBN 978-0-19-927634-9. Archived from the original on 2017-02-28. Retrieved 2016-07-25.
Lawson, Mark V. (17 September 2003). Finite Automata. CRC Press. pp. 98–100. ISBN 978-1-58488-255-8. Archived from the original on 27 February 2017. Retrieved 25 July 2016.
Kleene 1951. Kleene, Stephen C. (1951). "Representation of Events in Nerve Nets and Finite Automata". In Shannon, Claude E.; McCarthy, John (eds.). Automata Studies (PDF). Princeton University Press. pp. 3–42. Archived (PDF) from the original on 2020-10-07. Retrieved 2017-12-10.
Leung, Hing (16 September 2010). "Regular Languages and Finite Automata" (PDF). New Mexico State University. Archived from the original (PDF) on 5 December 2013. Retrieved 13 August 2019. The concept of regular events was introduced by Kleene via the definition of regular expressions.
Kernighan, Brian (2007-08-08). "A Regular Expressions Matcher". Beautiful Code. O'Reilly Media. pp. 1–2. ISBN 978-0-596-51004-6. Archived from the original on 2020-10-07. Retrieved 2013-05-15.
Ritchie, Dennis M. "An incomplete history of the QED Text Editor". Archived from the original on 1999-02-21. Retrieved 9 October 2013.
Aho & Ullman 1992, 10.11 Bibliographic Notes for Chapter 10, p. 589. Aho, Alfred V.; Ullman, Jeffrey D. (1992). "Chapter 10. Patterns, Automata, and Regular Expressions" (PDF). Foundations of Computer Science. Archived from the original on 2020-10-07. Retrieved 2013-12-14.
Raymond, Eric S. citing Dennis Ritchie (2003). "Jargon File 4.4.7: grep". Archived from the original on 2011-06-05. Retrieved 2009-02-17.
"New Regular Expression Features in Tcl 8.1". Archived from the original on 2020-10-07. Retrieved 2013-10-11.
"Documentation: 9.3: Pattern Matching". PostgreSQL. Archived from the original on 2020-10-07. Retrieved 2013-10-12.
Wall, Larry (2006). "Perl Regular Expressions". perlre. Archived from the original on 2009-12-31. Retrieved 2006-10-10.
Wall (2002) Wall, Larry (2002). "Apocalypse 5: Pattern Matching". Archived from the original on 2010-01-12. Retrieved 2006-10-11.
"GRegex – Faster Analytics for Unstructured Text Data". grovf.com. Archived from the original on 2020-10-07. Retrieved 2026-04-20.
"CUDA grep". bkase.github.io. Archived from the original on 2020-10-07. Retrieved 2019-10-22.
Gelade & Neven (2008, p. 332, Thm.4.1) Gelade, Wouter; Neven, Frank (2008). Succinctness of the Complement and Intersection of Regular Expressions. Proceedings of the 25th International Symposium on Theoretical Aspects of Computer Science (STACS 2008). pp. 325–336. arXiv:0802.2869. Archived from the original on 2011-07-18. Retrieved 2009-06-15.
Gruber & Holzer (2008) Gruber, Hermann; Holzer, Markus (2008). Finite Automata, Digraph Connectivity, and Regular Expression Size (PDF). Proceedings of the 35th International Colloquium on Automata, Languages and Programming (ICALP 2008). Lecture Notes in Computer Science. Vol. 5126. pp. 39–50. doi:10.1007/978-3-540-70583-3_4. ISBN 978-3-540-70582-6. Archived (PDF) from the original on 2011-07-11. Retrieved 2011-02-03.
Based on Gelade & Neven (2008), a regular expression of length about 850 such that its complement has a length about 2³² can be found at File:RegexComplementBlowup.png. Gelade, Wouter; Neven, Frank (2008). Succinctness of the Complement and Intersection of Regular Expressions. Proceedings of the 25th International Symposium on Theoretical Aspects of Computer Science (STACS 2008). pp. 325–336. arXiv:0802.2869. Archived from the original on 2011-07-18. Retrieved 2009-06-15.
Redko, V.N. (1964). "On defining relations for the algebra of regular events". Ukrainskii Matematicheskii Zhurnal (in Russian). 16 (1): 120–126. Archived from the original on 2018-03-29. Retrieved 2018-03-28.
"Perl Regular Expression Documentation". perldoc.perl.org. Archived from the original on December 31, 2009. Retrieved November 5, 2024.
"Regular Expression Syntax". Python 3.5.0 documentation. Python Software Foundation. Archived from the original on 18 July 2018. Retrieved 10 October 2015.
"Essential classes: Regular Expressions: Quantifiers: Differences Among Greedy, Reluctant, and Possessive Quantifiers". The Java Tutorials. Oracle. Archived from the original on 7 October 2020. Retrieved 23 December 2016.
"Atomic Grouping". Regex Tutorial. Archived from the original on 7 October 2020. Retrieved 24 November 2019.
Cezar Câmpeanu; Kai Salomaa & Sheng Yu (Dec 2003). "A Formal Study of Practical Regular Expressions". International Journal of Foundations of Computer Science. 14 (6): 1007–1018. doi:10.1142/S012905410300214X. Archived from the original on 2015-07-04. Retrieved 2015-07-03. Theorem 3 (p.9)
"Perl Regular Expression Matching is NP-Hard". perl.plover.com. Archived from the original on 2020-10-07. Retrieved 2019-11-21.
Wandering Logic. "How to simulate lookaheads and lookbehinds in finite state automata?". Computer Science Stack Exchange. Archived from the original on 7 October 2020. Retrieved 24 November 2019.
Cox (2007) Cox, Russ (2007). "Regular Expression Matching Can Be Simple and Fast". Archived from the original on 2010-01-01. Retrieved 2008-04-27.
Laurikari (2009) Laurikari, Ville (2009). "TRE library 0.7.6". Archived from the original on 2010-07-14. Retrieved 2009-04-01.
"gnulib/lib/dfa.c". Archived from the original on 2021-08-18. Retrieved 2022-02-12. If the scanner detects a transition on backref, it returns a kind of "semi-success" indicating that the match will have to be verified with a backtracking matcher.
Navarro, Gonzalo (10 November 2001). "NR-grep: a fast and flexible pattern-matching tool" (PDF). Software: Practice and Experience. 31 (13): 1265–1312. doi:10.1002/spe.411. S2CID 3175806. Archived (PDF) from the original on 7 October 2020. Retrieved 21 November 2019.
"travisdowns/polyregex". GitHub. 5 July 2019. Archived from the original on 14 September 2020. Retrieved 21 November 2019.
"Vim documentation: pattern". Vimdoc.sourceforge.net. Archived from the original on 2020-10-07. Retrieved 2013-09-25.
"UTS#18 on Unicode Regular Expressions, Annex A: Character Blocks". Archived from the original on 2020-10-07. Retrieved 2010-02-05.
Horowitz, Bradley (24 October 2011). "A fall sweep". Google Blog. Archived from the original on 21 October 2018. Retrieved 4 May 2019.
The character 'm' is not always required to specify a Perl match operation. For example, m/[^abc]/ could also be rendered as /[^abc]/. The 'm' is only necessary if the user wishes to specify a match operation without using a forward-slash as the regex delimiter. Sometimes it is useful to specify an alternate regex delimiter in order to avoid "delimiter collision". See 'perldoc perlre Archived 2009-12-31 at the Wayback Machine' for more details.
Conway, Damian (2005). "Regular Expressions, End of String". Perl Best Practices. O'Reilly. p. 240. ISBN 978-0-596-00173-5. Archived from the original on 2020-10-07. Retrieved 2017-09-10.

Regular expression (English Wikipedia)

157.5 (Global: low place; English: low place)

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nmsu.edu (Global: 9,083rd place; English: 6,016th place)

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opengroup.org (Global: 6,630th place; English: 5,295th place)

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oracle.com (Global: 2,532nd place; English: 1,847th place)

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princeton.edu (Global: 802nd place; English: 528th place)

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python.org (Global: 4,399th place; English: 3,941st place)

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rand.org (Global: 3,236th place; English: 2,152nd place)

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semanticscholar.org (Global: 15th place; English: 8th place)

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sourceforge.net (Global: 1,842nd place; English: 1,520th place)

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stackexchange.com (Global: 4,114th place; English: 3,027th place)

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stanford.edu (Global: 194th place; English: 182nd place)

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tufts.edu (Global: 192nd place; English: 165th place)

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uchile.cl (Global: 2,618th place; English: 4,466th place)

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unicode.org (Global: 691st place; English: 581st place)

web.archive.org (Global: 1st place; English: 1st place)

archive-it.org (Global: 1,292^nd place; English: 869^th place)

archive.org (Global: 6^th place; English: 6^th place)

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books.google.com (Global: 3^rd place; English: 3^rd place)

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gnu.org (Global: 1,901^st place; English: 1,743^rd place)

googleblog.blogspot.com (Global: 6,935^th place; English: 8,461^st place)

hdl.handle.net (Global: 66^th place; English: 34^th place)

howtogeek.com (Global: 8,729^th place; English: 6,329^th place)

ietf.org (Global: 731^st place; English: 625^th place)

nmsu.edu (Global: 9,083^rd place; English: 6,016^th place)

opengroup.org (Global: 6,630^th place; English: 5,295^th place)

oracle.com (Global: 2,532^nd place; English: 1,847^th place)

princeton.edu (Global: 802^nd place; English: 528^th place)

python.org (Global: 4,399^th place; English: 3,941^st place)

rand.org (Global: 3,236^th place; English: 2,152^nd place)

rfc-editor.org (Global: 747^th place; English: 325^th place)

scribd.com (Global: 467^th place; English: 428^th place)

semanticscholar.org (Global: 15^th place; English: 8^th place)

sourceforge.net (Global: 1,842^nd place; English: 1,520^th place)

stackexchange.com (Global: 4,114^th place; English: 3,027^th place)

stanford.edu (Global: 194^th place; English: 182^nd place)

tufts.edu (Global: 192^nd place; English: 165^th place)

uchile.cl (Global: 2,618^th place; English: 4,466^th place)

unicode.org (Global: 691^st place; English: 581^st place)

web.archive.org (Global: 1^st place; English: 1^st place)