#namely how can I pick only the topmost with this subroutine
#besides some reference error that I encounter.

sub print_zHoA {
    my ($HoA) = @_;
    foreach my $mc (sort {$HoA{$a}[0] <=> $HoA{$b}[0]} keys %$HoA){
      print "$mc $HoA{$mc}[0]:\n";
      foreach my $i (0.. $#{$$HoA{$mc}}) {
        print "$$HoA{$mc}[$i]->[0],$$HoA{$mc}[$i]->[1],$$HoA{$mc}[$i]->[2]";
       }
        print "\n";
    }
}