use warnings;
use strict;

use Data::Dumper;

my $href = {
    a => 1,
    b => [
            2,
            3,
         ],
    c => {
            25 => 'y',
            26 => 'z',
         },
    d => 4,
};

my $memfile;

open my $mfh, '>', \$memfile or die $!;
print $mfh Dumper($href);
close $mfh;

print $memfile;