Perhaps AnyEvent or IO::Async might be helpful.

Alternatively, have a look at fork and wait.

But ithreads are now discouraged, which leaves you with fork. You might try opening all 6 files at once and writing one block at a time to each of them -- that might work ok, depending on how your os does buffering.

No it doesn't, that just nonsense, don't spread it around Re^2: Splitting large array for threads.

And who are you that we should take your word for it, even though you provide no reasoning behind your statement?

I assumed the OP was writing several different files to several different USB drives, in which case you might be able to get an improvement.

You might as well give the module Many Core Engines (MCE) a go.

The MCE 1.515 was moved to back pan some time back. Here is the URL.

https://metacpan.org/pod/MCE

There is another example Re^4: Using MCE to write to multiple files..

The MCE->sendto method is available. A nice thing is that MCE caches the file handle, therefore only opening the file handle once during the run. The sendto method appends, thus the reason for unlink.

Below, using the Flow model as input_data is not required to run.

   use MCE::Flow max_workers => 8;

   my $file1 = "/path/to/file1.txt";
   my $file2 = "/path/to/file2.txt";

   unlink $file1 if -e $file1;
   unlink $file2 if -e $file2;

   mce_flow sub {
      my $wid = MCE->wid;

      if (MCE->wid % 2 == 0) {
         MCE->sendto("file:$file1", "sunny day from $wid\n");
      } else {
         MCE->sendto("file:$file2", "raining day from $wid\n");
      }
   };
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Another way is via MCE->print, MCE->printf, MCE->say. MCE serializes data from workers to the manager process. The output is done by the manager process. These methods are beneficial when many workers write to same file simultaneously.

   use MCE::Loop chunk_size => 1, max_workers => 8;

   my @input = (100..199);

   open my $fh_1, '>', '/path/to/file1.txt';
   open my $fh_2, '>', '/path/to/file2.txt';

   mce_loop {
      my ($mce, $chunk_ref, $chunk_id) = @_;

      if ($chunk_id % 2 == 0) {
         MCE->say($fh_1, "id: $chunk_id: input $_");
      } else {
         MCE->say($fh_2, "id: $chunk_id: input $_");
      }

   } @input;

   close $fh_1;
   close $fh_2;
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In case the reader missed it, the syntax for mce_flow requires the sub in front of the opening brace unlike mce_loop which takes a block. The reason is that mce_flow can take many anonymous blocks; e.g. mce_flow sub { ... }, sub { ... }.