regex::is_match, find, find_all, replace, replace_all, split, captures
all called Regex::new(pattern) per invocation. A script doing
`regex::is_match("\\d+", x)` in a tight loop paid the compile every
iteration. Regex compile dominates is_match on short strings.
Add a thread-local LruCache<String, Arc<Regex>> (cap 128). The
compile helper now memoises by pattern string, returning Arc<Regex>
on hit. Cap is well above what any sensible script uses but bounded
enough to keep memory predictable on long-running threads.
AUDIT.md anchor: F-P-014.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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