key1            key2            key3            key4            key5
$data{key1}[0]  $data{key2}[0]  $data{key3}[0]  $data{key4}[0]  $data{key5}[0]
$data{key1}[1]  $data{key2}[1]  $data{key3}[1]  $data{key4}[1]  $data{key5}[1]
$data{key1}[2]  $data{key2}[2]  $data{key3}[2]  $data{key4}[2]  $data{key5}[2]
...

##</code><code>##

my $col_width = 20;
my @keys      = sort keys %data;
my $p_format  = join(" " => ("%${col_width}s") x @keys) . "\n";

## $p_format would be "%20s %20s %20s ... %20s\n", so the columns will
## line up even if the data strings are different sizes

printf $p_format, @keys;

my $i = 0;
LOOP: {
    ## important part: pull out the ith entry in each array
    my @ith_data = map { $data{$_}[$i] || "" } @keys;

    ## you mentioned the data strings end in \n
    chomp @ith_data; 

    printf $p_format, @ith_data;

    $i++;

    ## loop again if any array has elements left
    for (@keys) {
        redo LOOP if exists $data{$_}[$i];
    }
}

##</code><code>##

my @keys = sort keys %data;
for my $i ( 0 .. $size-1 ) {
    my @ith_data = map { $data{$_}[$i] || "" } @keys;
    chomp @ith_data; 
    print "@ith_data\n";
}