@p{'eyes', 'hair', 'etc'} =();

##</code><code>##

  my %p;
  $p{$_} = undef for qw(eyes hair etc);

##</code><code>##

  @p{ 'eyes', 'hair', 'etc' }

##</code><code>##

  sub do_head {
       my($heading, @data) = @_;

      return "<h4>$heading</h4>" if grep { defined($_) } @data;
      return "";
  }