use strict;
use Data::Dumper;
my %hash;

%hash = (key1 => [1],
         key2 => [1],
         key3 => [1]);

##</code><code>##

         
push(@{$hash{key2}},4);
push(@{$hash{key3}},8);
push(@{$hash{key1}},7);
push(@{$hash{key2}},9);
$hash{key4} = [8];
push(@{$hash{key2}},9);
push(@{$hash{key3}},2);


##</code><code>##

foreach (hash key){
  my $last_one = pop(@{$hash{$_}}); 
  print "$_ $last_one \n";
}

so that rtesult is going to be:

key3 2
key2 9
key4 8
key1 7

and in next iteration :

key2 9
key3 8
key1 1