Why are you calling exec in your child ?

An alternative approach may be to use Parallel::ForkManager. then your code could look something like this

   my $pm = new Parallel::ForkManager(10);

   for my $count (1..10) {
      $pm->start and next; # do the fork

      sub1($count,$lines,\@cna);

      $pm->finish; # do the exit in the child process
  }

  $pm->wait_all_children;
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