sub _merge_arrays {
   my ( $left, $right ) = ( shift, shift );
   if( ref $left ne 'ARRAY' || ref $right ne 'ARRAY' ) {
       carp 'Arguments for _merge_arrays must be array references';
       return;
   }

   my $length = $#$left;
   $length = $#$right if ($#$right > $length);
     my @newarray;
   for (my $num = 0; $num <= $length; $num++) {
       if ( defined $left->[$num] && defined $right->[$num] ) {
           @newarray[ $num ]
               = merge ( $left->[ $num ], $right->[ $num] );
       }
       elsif ( defined $left->[$num] && !(defined $right->[$num]) ) {
           @newarray[ $num ]
               = $left->[ $num ];
       }
       elsif ( !(defined $left->[$num]) && defined $right->[$num] ) {
           @newarray[ $num ]
               = $right->[ $num ];
       }
       else {
           $newarray[$num] = $clone_behavior
               ? _my_clone( $left->[$num] ) : $left->[$num];
       }
   }#for     return \@newarray;
}