PCRE2 Perl-Compatible Regex

PCRE2 (Perl Compatible Regular Expressions version 2) is a C library implementing regex pattern matching using Perl 5 syntax and semantics. Originally created by Philip Hazel at the University of Cambridge in 1997 (as PCRE), PCRE2 is the successor with a cleaner API. With over 1,500 stars as of 2026, PCRE2 serves as the default regex engine for PHP, Apache, nginx, Postfix, Exim, and countless applications. Key features include: Perl 5 compatibility (supporting backreferences, look-ahead/behind assertions, named subpatterns, atomic groups, and conditional subpatterns), multi-width API (8-bit, 16-bit, and 32-bit character modes supporting ASCII, UTF-8, UTF-16, and UTF-32), JIT compilation (compiling patterns to native machine code via SLJIT for 5-10x faster matching, supporting x86, ARM, MIPS, PowerPC, and S390x), Unicode support (full property support via backslash-p syntax, case folding, and grapheme cluster segmentation), DFA matching (alternative engine using deterministic finite automata for linear-time matching without backtracking), callouts (invoking C callbacks during matching for custom processing), serialization (saving and loading compiled patterns for reuse), substitution (find-and-replace with backreferences and named groups), JIT stack management, and pcre2grep (a grep-like CLI built on PCRE2).