my $D = pack '(.* A*)*', map { $_, "foo" }
            77777, 1234000000, 2345000111 ;
my $p = 0;

{
    $p = index($D, "foo", $p);
    warn "p=$p\n";
    redo if ++$p;
}
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Segfaults for me with perl5.20.2 and earlier. Works with 5.22.0. All are x86_64-linux-thread-multi.