Filter lists carry a few hundred rules written as JavaScript regex
literals (24 in EasyList, 165 in uBO's badware list); they parsed but
were dropped as unsupported. PCRE2 reads that syntax as-is, `\/` and
friends included, its compiled patterns are immutable so the one
blocker shared by every HTTP client thread can run them, and 10.48
ships a build.zig for 0.16, so it is wired like sqlite3.
`Regex.Context` routes every PCRE2 allocation through the blocker's
allocator, which puts the compiled patterns under the test runner's
leak detection, and caps match and depth so a broken pattern costs a
false negative rather than a stalled request. As in uBO, a regex
tests the raw URL with the case-insensitive flag unless `$match-case`.
Regex filters are still never tokenized: they ride the fallback bucket.
Adrià Arrufat
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