sub iter { 
  my $href = shift; 
  my $level = shift; 
  local $_; 

  foreach (keys %{$href}) { 
    if (ref($href->{$_})) { 

        iter($href->{$_}, $level+1); 
    } 
    else { 
      print ' ' x $level; 
      print "$_\n"; 
    } 
  } 
} 

iter(\%unique, 0);