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Perl Compatible Regular Expressions
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<p>Perl Compatible Regular Expressions (PCRE) is a <a href="/facts/Library_(computing)/xRzL3P7q">library</a> written in <a href="/facts/C_(programming_language)/Ky2No763">C</a>, which implements a <a href="/facts/Regular_expression/KFL3veHX">regular expression</a> engine, inspired by the capabilities of the <a href="/facts/Perl/fx31kjlT">Perl programming language</a>. <a href="/facts/Philip_Hazel/2mus7WJ5">Philip Hazel</a> started writing PCRE in summer 1997. PCRE's syntax is much more powerful and flexible than either of the <a href="/facts/Regular_expression/KFL3veHX">POSIX regular expression</a> flavors (BRE, ERE) and than that of many other regular-expression libraries. </p><p>While PCRE originally aimed at feature-equivalence with Perl, the two implementations are not fully equivalent. During the PCRE 7.x and Perl 5.9.x phase, the two projects coordinated development, with features being ported between them in both directions. </p><p>In 2015, a fork of PCRE was released with a revised programming interface (API). The original software, now called PCRE1 (the 1.xx–8.xx series), has had bugs mended, but no further development. As of 2020<a href="https://en.wikipedia.org/w/index.php?title=Perl_Compatible_Regular_Expressions&action=edit">[update]</a>, it is considered obsolete, and the current 8.45 release is likely to be the last. The new PCRE2 code (the 10.xx series) has had a number of extensions and coding improvements and is where development takes place. </p><p>A number of prominent <a href="/facts/Open-source_software/HzTaB8E9">open-source programs</a>, such as the <a href="/facts/Apache_HTTP_Server/tcmWYYUq">Apache</a> and <a href="/facts/Nginx/AlTYUuTp">Nginx</a> HTTP servers, and the <a href="/facts/PHP/vU6YRJX0">PHP</a> and <a href="/facts/R_(programming_language)/LSrkr8K8">R</a> scripting languages, incorporate the PCRE library; proprietary software can do likewise, as the library is BSD-licensed. As of Perl 5.10, PCRE is also available as a replacement for Perl's default regular-expression engine through the re::engine::PCRE module. </p><p>The library can be built on Unix, Windows, and several other environments. PCRE2 is distributed with a POSIX C wrapper, several test programs, and the utility program pcregrep/pcre2grep that is built in tandem with the library. </p>