[Issue 18600] Regex performance enhancement for repeated matchFirst calls

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18600

--- Comment #1 from github-bugzilla at puremagic.com ---
Commit pushed to master at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/4318073f40ae3e82ac1847da5e037ab2f091d6fc
Fix issue 18600 Revamp std.regex caching for matchFirst case

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