Possessive quantifiers are a way to prevent the regex engine from trying all permutations. This is primarily useful for performance reasons. You can also use possessive quantifiers to eliminate certain matches.
This tutorial will teach you how to create your own regular expressions, starting with the most basic regex concepts and ending with the most advanced and specialized capabilities.
Validate and benchmark your .NET regular expressions here in this lightweight Silverlight application. Your regular expression matches will be highlighted as you type.
Regex validation. Test PHP, Perl or Javascript regular expression - instant live AJAX online testing tool (regex validator). Search and replace with RegExp.
This page provides a basic tutorial on understanding, creating and using regular expressions in Perl. It serves as a complement to the reference page on regular expressions perlre. Regular expressions are an integral part of the m//, s///, qr// and split operators and so this tutorial also overlaps with "Regexp Quote-Like Operators" in perlop and "split" in perlfunc.
Regular expressions is the term used for a codified method of searching invented or defined by the American mathematician Stephen Kleene. The syntax (language format) described is compliant with extended regular expressions (EREs) defined in IEEE POSIX 1003.2 (Section 2.8). EREs are now commonly supported by Apache, PHP4, Javascript 1.3 , MS Visual Studio, MS Frontpage, most visual editors, vi, emac, the GNU family of tools (including grep, awk and sed) as well as many others. Extended Regular Expressions (EREs) will support Basic Regular Expressions (BREs are essentially a subset of EREs). Most applications, utilities and laguages that implement RE's extend the capabilities defined. The appropriate documentation should always be consulted.
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Y. Li, R. Krishnamurthy, S. Raghavan, S. Vaithyanathan, and H. Jagadish. Proceedings of the 2008 Conference on Empirical Methods in Natural Language Processing, page 21--30. Honolulu, Hawaii, Association for Computational Linguistics, (October 2008)