Thanks Monks, I have solved by using Forcearray

$xmlconfig = XMLin($xml,ForceArray => [qw{batch-member}]);
my $count= (@{$xmlconfig->{order}->{'item-info'}->{batch}->{'batch-mem
+ber'}});
#print $count;

for ($i=0; $i<=$count; $i++ ){
  my $batch_aid = $xmlconfig->{order}->{'item-info'}->{batch}->{'batch
+-member'}->[$i]->{'aid'};
  my $batch_pii = $xmlconfig->{order}->{'item-info'}->{batch}->{'batch
+-member'}->[$i]->{'pii'};
  my $batch_newpii=$batch_pii;
  $batch_newpii=~s/[^A-z0-9]//gi;
  
  my $batch_pit = $xmlconfig->{order}->{'item-info'}->{batch}->{'batch
+-member'}->[$i]->{'pit'};
  my $batch_doi = $xmlconfig->{order}->{'item-info'}->{batch}->{'batch
+-member'}->[$i]->{'doi'};

  $orderin{$batch_aid} = { 'pit'  => $batch_pit,
                           'pii'  => $batch_pii,
                           'doi'  => $batch_doi,
                         };
  my $Eextra='';
  $i++;
  $orderin{subitem}='Yes';


}
[download]