I think it's simpler, the pattern isn't empty, because (?:...) is always part of the pattern. Meta characters count too.

This idiom is meant to be used as s//something/ in complicated parsing, kind of inherited from sed/awk IIRC.

You should also be aware that a genuinely empty pattern IS always matching. In your case the replacement is just invisible because empty.

So I'd rather prefer to make this explicit and self documenting

  • s/$extra// if $extra

    Nowadays I doubt there are more than a fraction of a percent of programmers knowing/using this feature.

    I'd really like to see a Perl version/feature to switch it off by default.

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

    In reply to Re^4: Strange Occurrence in Substitution Statement by LanX
    in thread Strange Occurrence in Substitution Statement by roho

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