my %old_gp = map {$gp1_a[$_] => $gp1_b[$_]} 0 .. $#gp1_a;
my %new_gp = map {$gp2_a[$_] => $gp2_b[$_]} 0 .. $#gp2_a;
                                                                                                                                       
                                                                                                                                       
my @diff=();
foreach (keys %new_gp)  {
        push (@diff, "$_ ")  unless exists $old_gp{$_};
}
                                                                                                                                       
print @diff;