Regex Flavors: How .NET, JavaScript, PCRE2, POSIX BRE/ERE and RE2 Differ, and Telling Globs from Regex
The same pattern works, fails or silently matches something else depending on the flavor: the Perl family (.NET, JavaScript, PCRE2) offers lookaround through backtracking, RE2 and Rust regex give it up for linear time, and POSIX picks the longest match. We run one probe list in five engines, show Prometheus's full-match =~ with promtool, and the difference between globs and regex with .gitignore and PowerShell.
15 Nov 2026
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16 min
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6
