Version 5.4.0 of GNU awk (gawk) has been released. This is a major release with a change in gawk's default regular-expression matcher: it now uses MinRX as the default regular-expression engine. This matcher is fully POSIX compliant, which the current GNU matchers are not. In particular it follows POSIX rules for finding the longest leftmost submatches. It is also more strict as to regular expression syntax, but primarily in a few corner cases that normal, correct, regular expression usage should not encounter. Because regular expression matching is such a fundamental part of awk/gawk, the original GNU matchers are still included in gawk. In order to use them, give a value to the GAWK_GNU_MATCHERS environment variable before invoking gawk. [...] The original GNU matchers will eventually be removed from gawk. So, please take the time to notice and report any issues in the MinRX matcher, so that they can be ironed out sooner rather than later. See the release announcement for additional