sub compare_arrays
{
  my ($first, $second) = @_;
  my %found;
  my @tmp;
  for my $elm (@$first) 
  {
    if(defined($elm) && grep{defined($_) && $elm eq $_}@$second && !$found{$elm})
    {
      push(@tmp,$elm);
      $found{$elm}++;
    }
  }
  return @tmp;
}