Looks like you need a sort function or block and to keep the previous (sorted) case in an up-scope variable, e.g.

my $prevCase = '';
for my $i (sort caseThenId (0..$#$var1) {
    my $case = $var1->[$i]{case};
    print "$case:"\n" if $case ne $prevCase;
    $prevCase = $case;
    print $var1->[$i]{id} . ") "
        . $var1->[$i]{name} . ", "
        . $var1->[$i]{degree} . "\n";
}

sub caseThenId {
    $var1->[$a]{case} cmp $var1->[$b]{case}
    or $var1->[$a]{id} cmp $var1->[$b]{id};
}
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Update: $var1 should be a reference to your array in the above example.