package MyMemory;

use strict;
use Storable qw(freeze thaw);
use BerkeleyDB;
use Fcntl qw(:DEFAULT);

use vars qw(@ISA @EXPORT @EXPORT_OK $VERSION);
 
require Exporter;
$VERSION=0.1;
@ISA=qw(Exporter);
@EXPORT=qw(get_memory set_memory);

my $filename = "/home/test/mem.db";


sub new {
  my $Proto = shift;
  my $Class = ref($Proto) || $Proto;
  
  my %Cache;
  my $env = new BerkeleyDB::Env(
      -Home  => '/tmp',
      -Flags => DB_INIT_CDB | DB_CREATE | DB_INIT_MPOOL,
     #-Cachesize => 23152000,
      )
      or die "can't create BerkelyDB::Env: $!";
  my $Obj = tie %Cache, 'BerkeleyDB::Btree',
     -Filename => $filename,
     -Flags    => DB_CREATE,
     -Mode     => 0640,
     -Env      => $env
     or die ("Can't tie to $filename: $!");

  my $Self = {
    Cache => \%Cache,
    Obj => $Obj
  };

  bless ($Self, $Class);
  return $Self;
}

my $bdbobj = new MyMemory(); 

sub get_memory {    
    my $Key=shift;
    return $bdbobj->get($Key);
}

sub set_memory {
    my $Key=shift;
    my %Value = @_;
    $bdbobj->set($Key,\%Value);
}

sub set {
  $_[0]->{Obj}->db_put( $_[1], freeze($_[2]) );
}

sub get {
  my $value;
  $_[0]->{Obj}->db_get( $_[1], $value );
  return thaw( $value );
}
 
1;
[download]

This is very strange code. Your class makes an object that is a reference to itself, and then does nothing with it. Don't make an object if you aren't going to use any methods. Put these things into globals instead.