open my $one ,"<","/var/www/html/piRNA_html/UNAFold/output_folder_1.txt" or die "Cannot open the file (ONE): $!";
  # Note the use of a block-scoped variable $one, 
  #   and "||" replaced by the low-precedence "or"
  #   and "$!" added to provide the OS error message corresponding to the failure
 @folder = <$one>;
close $one;