my $counter;

for ($counter = 1; $counter <= 3; $counter++) {
  $pid = fork();
  if ($pid) {
    $child{$pid} = $counter;
  } else {
    exec "perl main.pl arg1 arg2";
    exit $counter; 
  } 
} 

while ($counter) {
 $doneproc = wait();
 $doneval = $? >> 8;
 $pid = fork();
 if ($pid) {
  $child{$pid} = $counter;
  $counter++;
 } else { 
  exec "perl main.pl arg1 arg2";
  exit $counter;
 } 
}