Change:

use Data::Dumper;
[download]

To:

use Data::Dumper;
$Data::Dumper::Useqq = 1;
[download]

$ perl -le'
use Data::Dumper;
$Data::Dumper::Useqq = 1;
my %h1;

$h1{(1, 1)} = 17;
$h1{(2, 2)} = 19;
$h1{("", 22)} = 23;
$h1{(22, "")} = 22;
my @h = (3, 4, 5);
$h1{(@h)} = 44;
print Dumper(\%h1);
'
$VAR1 = {
          "2\0342" => 19,
          "1\0341" => 17,
          "\03422" => 23,
          "22\34" => 22,
          "3" => 44
        };
[download]

Or change the value of $;:

$ perl -le'
use Data::Dumper;                          
my %h1;
$; = "--";

$h1{(1, 1)} = 17;
$h1{(2, 2)} = 19;
$h1{("", 22)} = 23;
$h1{(22, "")} = 22;
my @h = (3, 4, 5);
$h1{(@h)} = 44;
print Dumper(\%h1);
'
$VAR1 = {
          '2--2' => 19,
          '--22' => 23,
          '3' => 44,
          '1--1' => 17,
          '22--' => 22
        };
[download]