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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 </ol?
String interpolation of variables only happens for literal regexes in the source code. So if the pattern is read from a file or database this isn't an issue.

Embedded code within a pattern is only allowed within the scope of use re 'eval'; otherwise trying to compile such a regex from a string will die at run time.

The third one is a genuine issue, in terms of both CPU and memory usage.


In reply to Re^2: Is it safe to use external strings for regexes? by dave_the_m
in thread Is it safe to use external strings for regexes? by stevieb

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