Note that all solutions presented sofar will only return non-overlapping greedy matches, not all matches as the requirement is. Say for instance, you're searching for fofo in fofofo. I count two matches, but anything using while ("fofofo" =~ /fofo/g) will only find 1. And if the pattern is (?:fo)+ there are 6 potential matches (3 from position 0, 2 from position 2, 1 from position 4).

Perhaps you are only interested in non-overlapping greedy matches, but that wasn't clear to me.

$_ = "fofofo";
/((?:fo)+)(?{ say "[$-[1], $+[1], $1]" })(*FAIL)/;
__END__
[0, 6, fofofo]
[0, 4, fofo]
[0, 2, fo]
[2, 6, fofo]
[2, 4, fo]
[4, 6, fo]
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