#!/usr/bin/perl
use strict;
use warnings;
use 5.010;

my $test1 = ['Birne','Apfel'];
my @test2 = ('Fred','Anna');
my %test3 = (foo => 'bar',abc => 'def');
my $test4 = 'string';
my $ref = [
    0,
    1,
    2,
    [$test1,\@test2,\%test3,\$test4],
];

if (defined $ref->[3]) {

    require Data::Dumper;
    local $Data::Dumper::Useqq;
    $Data::Dumper::Useqq = 1;
    local $Data::Dumper::Sortkeys;
    $Data::Dumper::Sortkeys = sub {
        my ($hash) = @_;
        return [(sort {$a =~ /^\d+$/ && $b =~ /^\d+$/ ? $a <=> $b : lc($a) cmp lc($b)} keys %$hash)];
    };

    foreach my $keyref (@{$ref->[3]}) {
        say Data::Dumper::Dumper($keyref);
    }
}