#! perl -w
use strict;
use Benchmark qw(cmpthese);

sub intersect (\@\@) {
    my ($aryRef1, $aryRef2) = @_;
    my %count;
    $count{$_}++ foreach @$aryRef1, @$aryRef2;
    return grep{ $count{$_} == 1 } keys %count;
}

my @array1 = (1 .. 28000);
my @array2 = (1..1000, 1..100); # create some duplicates with duplicates

my %hashBase;
@hashBase{@array1} = undef;

sub faq {
	my @dup = intersect( @array1, @array2 );
}
sub hash {
	my %hashAry;
	@hashAry{@array1} = undef;
    my @dup = delete @hashAry{@array2};
}
sub prehash {
    my %hashAry = %hashBase;
	my @dup = delete @hashAry{@array2};

}
sub hash_lret {
	my %hashAry;
	@hashAry{@array1} = undef;
	my @dup = delete @hashAry{@array2};
    return keys %hashAry;
}

sub prehash_lret {
    my %hashAry = %hashBase;
	my @dup = delete @hashAry{@array2};
	return keys %hashAry;
}

sub grepped {
	my %reject;
	$reject{$_} = 1 for @array2;
    my @clean=grep !$reject{$_}, @array1;
}

cmpthese 100,{
              faq          => \&faq,
              hash         => \&hash,
              prehash      => \&prehash,
              hash_lret    => \&hash_lret,
              prehash_lret => \&prehash_lret,
              grepped      => \&grepped,
             };