Select Code to Download

use Fcntl qw( LOCK_EX O_RDWR O_CREAT SEEK_SET );

...
seek($fh, 0, SEEK_SET);
print($fh "$index\n");
#truncate($fh, tell($fh));

my $qfn = '/tmp/myfile.index';

...
   or die("Can't create \"$qfn\": $!\n");

print($fh "$index\n");