use strict;
package Test;

sub new {
  my $self = {};
  bless $self;
  return $self;
}

package main;

my $obj1 = Test->new();
my $obj2 = Test->new();
my $obj3 = Test->new();

$obj1->{DATE}="2005-01-01";
$obj2->{DATE}="2004-12-20";
$obj3->{DATE}="2005-01-02";


my @list = ($obj1,$obj2,$obj3);

print $_->{DATE},"\n" for sort {$a->{DATE} <=> $a->{DATE}} @list;
_ _ END _ _ 
2005-01-01
2004-12-20
2005-01-02