#! perl -sw
use strict;
use Benchmark::Timer;
my $timer = Benchmark::Timer->new(skip => 1);

local $\=$/;

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

my @aryBase = (1 .. 28000);
my %hashBase;
@hashBase{@aryBase} = undef;

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

for (0..100){
	my @array1 = @aryBase;
	$timer->start('faq');
	my @dup = intersect( @array1, @array2 );
	$timer->stop('faq');
}

for (0..100){
	my %hashAry = %hashBase;
	$timer->start('delete');
	my @dup = delete @hashAry{@array2};
	$timer->stop('delete');
}

$timer->report;

@aryBase = intersect( @aryBase, @array2 );
print '\@aryBase contains ', scalar @aryBase, ' elements after intersect';

delete @hashBase{@array2};
print '\@hashBase contains ', scalar keys %hashBase, ' elements after intersect';

__END__
#output
C:\test>207632
100 trials of faq (103.692s total), 1.037s/trial

100 trials of delete (881.000ms total), 8.810ms/trial

\@aryBase contains 27000 elements after intersect
\@hashBase contains 27000 elements after intersect

C:\test>