Are you sure that's what the textbook says? Anyway, the following works:
sub double_for {
    $CODE_REFERENCE = $_[0];
    for $i (1..$row_count) {
        for $j (1..$col_count) {
            &$CODE_REFERENCE($i, $j);
        }
    }
}

double_for(\&mysub);

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In reply to Re: In Search of a Smarter Sub by cdarke
in thread In Search of a Smarter Sub by Petras

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