...
  my $pid = wait;
  if ($pid == $pid1) {
    ...
    $pid1 = -1; # indicate child1 has been reaped
  }
...

##</code><code>##

while (1) {
  my $pid = wait;
  last if $pid < 0;
  if ($pid == $pid1) { ... }
  elsif ($pid == $pid2) { ... }
}