foreach my $grade ( 4, 8, 45, 48, 50, 51, 57, 60, 64, 66 , 90, 91, 99, 100) {
    my $chopped = _chop_grade($grade);
    my $rounded = _round_grade($grade);

    my $grade_chopped = _convert_grade($chopped);
    my $grade_rounded = _convert_grade($rounded);

    print "${grade}: ${rounded}/${grade_rounded} (Rounded) " .
        "- ${chopped}/${grade_chopped} (Chopped)\n";
}