Depending on how nasty your users are, allowing arbitrary regular expressions is an unwise choice. The following regex is valid but will use up lots of CPU:

"aaaaaaaaaaaaaaaaaaaaaaaaaaaaa" =~ /a*a*a*b/

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If you can come up with a whitelist of allowed regexes, that would improve things, or maybe consider running the regex search as a time-limited subprocess.

In reply to Re: Is it safe to use external strings for regexes? by Corion
in thread Is it safe to use external strings for regexes? by stevieb

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