That's the most useless run_on_finish possible. Worse than none at all.

#!/usr/bin/perl

use warnings;
use strict;

use Parallel::ForkManager qw( );

use constant MAX_WORKERS => 10;

sub work {
    my ($client) = @_;
    print("$client start...\n");
    sleep(3 + int(rand(2)));
    print("$client done.\n");
}

{
   my $pm = new Parallel::ForkManager(MAX_WORKERS);

   # Optional.
   $pm->run_on_finish(sub {
      my ($pid, $exit, $ident, $signal, $core) = @_;
      if ($signal) {
         print("Client $ident killed by signal $signal.\n");
      }
      elsif ($exit) {
         print("Client $ident exited with error $error.\n");
      }
      else {
         print("Client $ident completed successfully.\n");
      }
   });

   for my $client (1..33){
      $pm->start($client) and next;
      work($client);
      $pm->finish();
   }

   $pm->wait_all_children();
}
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