I personally still use system /ssh -i $key -h $host/ for perl scripts although using other ways specified (Net::SSH::Perl) might work better for you. I have found that I still like to use system /ssh $blah/ because I am still a fan of pwless SSH keys because of the way I have the security of my network layed out (and I am sure that a lot of people would argue my use of this, but this isn't the time or the place for that).

However, I have found that when I need to have multiple connections or do multiple time intensive things simultaneously that I use Parallel::ForkManager. It just forks off processes and lets you set the max number of processes that you would like to allow to run continuously.

 # Begin ForkManager
 my $_max_procs = 5;
 $_pm = new Parallel::ForkManager($_max_procs);

 # Log at process fork
 $_pm ->run_on_start(
   sub { my ($pid, $host) = @_;
     print "Forking process PID: $pid\n";
   }
 );

 # Log at process copmletion
 $_pm ->run_on_finish(
   sub { my ($pid, $exit_code, $host) = @_;
     print "Finishing up process PID: $pid\n";
   }
 );

 $_pm->run_on_wait(
   sub { print "Waiting for children to finish.\n" }, 5.0 );

foreach my $ssh_host (keys %{$ssh_host_list}) {
  # Fork off the children and get going on the queries
  my $pid = $_pm->start($ssh_host) and next;

  # do script stuff here

  # Closing the forked process
  $_pm->finish;
}

# Ensure all children have finished
$_pm->wait_all_children;
exit(1);
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