my @a = (0,1,2,3,4,5, 6, 7, 8 );
my @b = (0,2,4,6,8,10,12,14,16);
my (@matches,@mismatch);

print "An iterative solution\n";
foreach $a (@a) {
   push @matches, $a if grep{$a == $_}@b;
}
foreach $a (@a) {
   push @mismatch, $a unless grep{$a == $_}@b;
}
print "The arrays share: @matches\n";
print "Unique elements in \@a: @mismatch\n";

print"\nA hash solution\n";
@matches = @mismatch = ();

map{$seen{$_}++}@b;
@matches  = grep{defined $seen{$_}}@a;
@mismatch = grep{!defined $seen{$_}}@a;

print "The arrays share: @matches\n";
print "Unique elements in \@a: @mismatch\n";