use Benchmark;

my $UID = 0;

my $uids = [];
my $msgs = [];

for (1..10000)
{
  UO->new;
}

my %pre_uid2msg = map { $_->uid => $_ } @$msgs;
timethese(-5,
  {
    original => sub {
      my %uid2msg     = map { $_->uid => $_ } @$msgs;
      return [ map { $uid2msg{$_} } @$uids ];
    },
    hashslice => sub {
      my %uid2msg     = map { $_->uid => $_ } @$msgs;
      return [ @uid2msg{ @$uids }];
    },
    original_pre => sub {
      return [ map { $pre_uid2msg{$_} } @$uids ];
    },
    hashslice_pre => sub {
      return [ @pre_uid2msg{ @$uids }];
    } 
  }
);

package UO;

sub new
{
  $UID += rand(1000);
  my $self = bless {uid => $UID}, shift();
  push(@$uids, $UID);
  push(@$msgs, $self);

  return $self;
}
 
sub uid
{
  my $self = shift;
  return $self->{uid};
}