use Bio::Tools::SiRNA;

     

  my $sirna_designer = Bio::Tools::SiRNA->new( -target => $bio_seq,
                                               -rules  => 'tuschl'
    );


  my @pairs = $sirna_designer->design;


  foreach $pair (@pairs)

 {
      my $sense_oligo_sequence = $pair->sense->seq;
      my $antisense_oligo_sequence = $pair->antisense->seq;

      # print out results
      print join ("\t", $pair->start, $pair->end, $pair->rank,
                  $sense_oligo_sequence, $antisense_oligo_sequence), "\n";
  }