my @data;
for ($i=1; $i<=$number; $i++) {
  open (LOOKUP, '<', "file$i");       
  while (<LOOKUP>) {
    chomp;
    my ($ref_name, $ref_id) = (split /\t/, $_)[3,4];
    $data[$i]{$ref_id} = $ref_name; 
  }
}