#!/usr/bin/perl

use strict;
use warnings;

my %dienste=(
"z" => {
   "y" => {
       "x" => {
           "fields" => {
               "a" => {
                   "order" => "03",
                   "content" => "n"
               },
               "b" => {
                   "order" => "02",
                   "content" => "u"
               },
               "c" => {
                   "order" => "01",
                   "content" => "h"
               },
               "d" => {
                   "order" => "04",
                   "content" => "d"
               }
           }    
       }
   }
}
);

my $hashref = $dienste{z}->{y}->{x}->{fields};
my @sorted = sort{$hashref->{$a}->{order} <=> $hashref->{$b}->{order} }keys %$hashref;

for my $key(@sorted){
    print sprintf "%s -- %s\n",$hashref->{$key}->{order}, $hashref->{$key}->{content};
}