> My question is whether this is safe to do or not

I'm not sure if you ask if your code or if foreign regexes "are safe".

In the latter case, there are three issues I'm aware of

  1. code injection by string interpolation, like /@{[ do_evil() ]}/
  2. code injection by regex, like /(?{ do_evil() })/
  3. exponential time regexes with excessive backtracking, something like /((x*)*)*/ IIRC ²

the first two cases might be solved by introspection/blacklisting regex-ops first, the latter probably only by experimenting with a hard limit on runtime.

NB: it's even possible to "hide" a BEGIN block inside a regex, we had this discussion about 10 years ago, I'll update a link. °

Edit: We had regularly similar discussions over the years, you might want to Super Search the archives.

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

updates

°) here --> Re: Vulnerabilities when editing untrusted code... (Komodo)

²) more at regex-explosive-quantifiers

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

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