# script 1: create the index
  use Bio::Index::Fasta; # using fasta file format
  $Index_File_Name = shift;
  $inx = Bio::Index::Fasta->new(
      -filename => $Index_File_Name,
      -write_flag => 1);
  $inx->make_index(@ARGV);

  # script 2: retrieve some files
  use Bio::Index::Fasta;
  $Index_File_Name = shift;
  $inx = Bio::Index::Fasta->new($Index_File_Name);
  foreach  $id (@ARGV) {
      $seq = $inx->fetch($id);  # Returns Bio::Seq object
      # do something with the sequence
  }