use strict;
my %hash = (
	a_one => 1, 
	b_two => 2,
	c_three => 3,
	d_four => 4,
	e_five => 5,
	f_six => 6,
	g_seven => 7,
	h_eight => 8,
	i_nine => 9,
	j_ten => 10
); 
my $pairs = (keys %hash);
my $counter = 0;
my $amount_to_print = int(0.20 * $pairs);

foreach my $key (reverse sort keys %hash) {
  if ($counter < $amount_to_print) {
    print $key, ' ', $hash{$key}, "\n";
  }
  else {
    last;
  }
  $counter++;
}


##</code><code>##

j_ten 10
i_nine 9