The regexp engine has never been re-entrant. It has only mattered since we have /(?{ })/ and /(??{ })/, before that, there was no way to start another match before the first one was finished. So even if it were re-entrant, you couldn't use the fact.

This: 

    /PAT1 (??{m!PAT2!}) PAT3/

[download]
is very likely to do unexpected things due to the regexp engine not being re-entrant.

In reply to Re^6: Regex fun by JavaFan
in thread Regex fun by Hena

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