sub DoStuff {
  my ($a, $b, $c) = @_;
  $a = defined $a ? $a : -1;
  $b = defined $b ? $b : -2;
  $c = defined $c ? $c : -3;

  print "A= $a\n";
  print "B= $b\n";
  print "C= $c\n";
}