sub sortmatrix(){
    for (my $i=0; $i<=$#matrix;$i++){
	my @resline = ( $i+1 );
	my @keys = ();
	for my $k ( sort { $matrix[$i]{$b} <=> $matrix[$i]{$a} } keys %{ $matrix[$i] } ) {
	    push @keys, $k;
	    push @resline, $matrix[$i]{$k};
	}
	push @resline, @keys;
	push @sorted, \@resline; # nb. pushing the reference not the array this time
	
    }
    
##</code><code>##

@sorted = sort {
	$b->[1] <=> $a->[1] ||
	    $b->[2] <=> $a->[2] ||
	    $b->[3] <=> $a->[3] ||
	    $b->[4] <=> $a->[4] ||
	    $a->[0] <=> $b->[0];
    } @sorted;
}

use Data::Dumper;
print Data::Dumper->Dump([ \@sorted ],[ qw/ *matrix / ]),"\n";


##</code><code>##

@sortedmatrix = (
                  [
                    4,
                    17,
                    0,
                    0,
                    0,
                    'C',
                    'A',
                    'T',
                    'G'
                  ],
                  [
                    5,
                    17,
                    0,
                    0,
                    0,
                    'A',
                    'T',
                    'C',
                    'G'
                  ],
                  [
                    6,
                    17,
                    0,
                    0,
                    0,
                    'T',
                    'A',
                    'C',
                    'G'
                  ],
                  [
                    7,
                    17,
                    0,
                    0,
                    0,
                    'G',
                    'A',
                    'T',
                    'C'
                  ],
                  [
                    9,
                    17,
                    0,
                    0,
                    0,
                    'C',
                    'A',
                    'T',
                    'G'
                  ],
                  [
                    10,
                    17,
                    0,
                    0,
                    0,
                    'C',
                    'A',
                    'T',
                    'G'
                  ],
                  [
                    11,
                    17,
                    0,
                    0,
                    0,
                    'G',
                    'A',
                    'T',
                    'C'
                  ],
                  [
                    12,
                    17,
                    0,
                    0,
                    0,
                    'G',
                    'A',
                    'T',
                    'C'
                  ],
                  [
                    14,
                    17,
                    0,
                    0,
                    0,
                    'C',
                    'A',
                    'T',
                    'G'
                  ],
                  [
                    15,
                    17,
                    0,
                    0,
                    0,
                    'A',
                    'T',
                    'C',
                    'G'
                  ],
                  [
                    16,
                    17,
                    0,
                    0,
                    0,
                    'T',
                    'A',
                    'C',
                    'G'
                  ],
                  [
                    17,
                    17,
                    0,
                    0,
                    0,
                    'G',
                    'A',
                    'T',
                    'C'
                  ],
                  [
                    3,
                    15,
                    2,
                    0,
                    0,
                    'A',
                    'G',
                    'T',
                    'C'
                  ],
                  [
                    13,
                    15,
                    2,
                    0,
                    0,
                    'G',
                    'A',
                    'T',
                    'C'
                  ],
                  [
                    18,
                    15,
                    2,
                    0,
                    0,
                    'T',
                    'C',
                    'A',
                    'G'
                  ],
                  [
                    1,
                    13,
                    4,
                    0,
                    0,
                    'G',
                    'A',
                    'T',
                    'C'
                  ],
                  [
                    8,
                    13,
                    4,
                    0,
                    0,
                    'C',
                    'T',
                    'A',
                    'G'
                  ],
                  [
                    19,
                    13,
                    4,
                    0,
                    0,
                    'C',
                    'T',
                    'A',
                    'G'
                  ],
                  [
                    2,
                    12,
                    5,
                    0,
                    0,
                    'G',
                    'A',
                    'T',
                    'C'
                  ],
                  [
                    20,
                    7,
                    7,
                    2,
                    0,
                    'T',
                    'C',
                    'G',
                    'A'
                  ]
                );