my @alphas = qw/ 9 4 3 2 22  13 7  140 95 278/;
my @betas  = qw/ 8 3 4 1 278 94 15 7   19 200/;

my @results;
my @sorted = sort { $a <=> $b } @alphas;

foreach my $beta ( @betas ) {
	my $index = binary_search( \@sorted, $beta );
	if ( defined $index ) {
		push @results, $beta;
	}
}

@results = sort { $a <=> $b } @results;
print "Binary search: @results\n";

sub binary_search {
	my ( $array, $target ) = @_;
	my ( $low, $high ) = ( 0, scalar @$array );

	while ( $low < $high ) {
		use integer;
		my $current = ( $low + $high ) / 2;
		if ( $array->[$current] < $target ) {
			$low = $current + 1;
		} else {
			$high = $current;
		}
	}
	if ( $low < @$array and $array->[$low] == $target ) {
		return $low;
	} else {
		return undef;
	}
}