my %cats;

  # .. loop to get a row
    # @row contains the retrieved row
    push $cats{ $row[1] }, $row[0]; # "Hash of arrays structure"
  # End of loop to get a row

##</code><code>##

  for  my $c (sort keys %cats){
     my $values = $cats{ $c };
     print "$c\t", join (" ", @$values), "\n";
  }

##</code><code>##

  my $ItemsPerLine=3;

  for  my $c (sort keys %cats){
     my $values = $cats{ $c };
     print "$c\t";
    for my $i(0..$#$values){
       $i % $ItemsPerLine==0 and print "\n\t";
       print  $values->[$i], " ";
    }
    print "\n" unless  $#$values % $ItemsPerLine==0;
  }