Please explain further what you intend to accomplish as an end result. Your code is actually fine albeit strange.

use strict;
use warnings;
use Data::Dumper;

my $value = "A\tB\tC\tD\tE\tF\t\t\t\t";
my @flds;
@flds = split(/\t/,$value);
$flds[16] = undef;
$flds[8] = 0;

print Dumper \@flds;

__END__
$VAR1 = [
          'A',
          'B',
          'C',
          'D',
          'E',
          'F',
          undef,
          undef,
          0,
          undef,
          undef,
          undef,
          undef,
          undef,
          undef,
          undef,
          undef
        ];
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PS: I see other replies, I am using Perl 5.20 Could be a bug.