Nice trick :-). Perhaps looking ahead only to immediately look back isn't necessary? (Same for other regexen, + all tests are OK):

my $re1 = qr{
    (?<target> x (?<digits> \d+ ) (?!\d) )
    (?<lookback>
        (?<=
            (?! (?<match> ab \g{digits} (?!\d) ) ) .
            (?=(?&lookback)) .
        |
            (?=(?&match)) . .
        )
    )
}msx;

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In reply to Re: Variable-Width Lookbehind (hacked via recursion) by vr
in thread Variable-Width Lookbehind (hacked via recursion) by haukex

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