push @holder, $key;
...
my @holder_sorted = sort { $hash{$a} <=> $hash{$b} } @holder;
print("@hash{@holder_sorted}\n"); 

##</code><code>##

my %holder;
...
$holder{$key} = $value;
...
my @holder_sorted = sort { $holder{$a} <=> $holder{$b} } keys @holder;
print("@holder{@holder_sorted}\n");