Three - is there a better way to go about doing this?

Yes. You are duplicating the functonality of Parallel::ForkManager. All you need is the following:

use strict;
use warnings;

use Parallel::ForkManager ();

use constant $MAX_PROCESSES => 3;

{
   my $pm = Parallel::ForkManager->new($MAX_PROCESSES);

   foreach my $fw (qw(fw1 fw2 fw3 fw4 fw5)) {
      my $pid = $pm->start and next; 

      exec "remotelogfile $fw logfile > /var/$fw.log"
         or die("Unable to launch \"remotelogfile $fw\": $!\n");

      # Will never reach this, but that's ok since it only calls exit.
      $pm->finish; # Terminates the child process
   }
}
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or just

use Parallel::ForkManager ();
my $pm = Parallel::ForkManager->new(3);
foreach my $fw (qw(fw1 fw2 fw3 fw4 fw5)) {
   $pm->start and next; 
   exec "remotelogfile $fw logfile > /var/$fw.log";
   die("Unable to launch \"remotelogfile $fw\": $!\n");
}
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