See: https://github.com/rust-lang/regex/blob/master/UNICODE.md#rl...
And then Unicode itself for more discussion on the topic: https://unicode.org/reports/tr18/#Simple_Loose_Matches
TR18 used to have a Level 3[1] with the kind of locale-specific custom tailoring support found in GNU's implementation of POSIX locales, but it was so fraught that it was retracted completely some years ago.
[1]: https://unicode.org/reports/tr18/#Tailored_Support
See: https://github.com/rust-lang/regex/blob/master/UNICODE.md#rl...
And then Unicode itself for more discussion on the topic: https://unicode.org/reports/tr18/#Simple_Loose_Matches
TR18 used to have a Level 3[1] with the kind of locale-specific custom tailoring support found in GNU's implementation of POSIX locales, but it was so fraught that it was retracted completely some years ago.
[1]: https://unicode.org/reports/tr18/#Tailored_Support