How much memory do you have? If you have enough, then this wd be a simple answer:

my @data_array = split('=' x 77, $data_string);
my @result_array;

for (@data_array) {
    @result_array = split('-' x 28, $_);
    if ($you_want_to_KEEP_the_last_comment) {
        print $result_array[$#result_array];
    }
    else {
        pop @result_array;
        print join('-' x 28,@result_array);
    }
}
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si in incipio non vinces, cape malleum maior
("if at first you don't succeed, use a bigger hammer")

§ George Sherston