my %item_count;
  %item_count{$_}++ foreach (@array);

##</code><code>##

  @result = grep {$item_count{$_} == 1} @array;

##</code><code>##

  my %item_count;
  %item_count{$_}++ for grep {/pattern/} @array
  @result = grep {$item_count{$_} <= 1} @array;

##</code><code>##

  @result = grep {($item_count{$_}||0) <= 1} @array;