my $pid1Complete = 0;
my $pid2Complete = 0;
my $pid3Complete = 0;
my $pid1 = system(1,"cmd...");
my $pid2 = system(1,"cmd...");
my $pid3 = system(1,"cmd...");

my $finishingPID = 0;
do {
	$finishingPID = wait();
	$rc = $?;
	if ($finishingPID == $pid1) 
	{
		$pid1Complete = 1;
		print "PID1 finished with return code $rc\n";
	}
	elsif ($finishingPID == $pid2)
	{
		$pid2Complete = 1;
		print "PID2 finished with return code $rc\n";
	}
	elsif ($finishingPID == $pid3)
	{
		$pid3Complete = 1;
		print "PID3 finished with return code $rc\n";
	}
} while (($pid1Complete == 0) || ($pid2Complete == 0) || ($pid3Complete == 0));