sub sub1 {
   #$x=shift;
   #$y=shift;
   print "$_[0] \n";
   $_[0]=8;
   $_[1]=9;

   print ("ENTRY x=$x y=$y\n");
   $x=3;
   $y=4;
   print ("EXIT x=$x y=$y\n");
}

$a=1;
$b=2;
print ("BEFORE a=$a b=$b \n");
sub1($a, $b);
print ("AFTER a=$a b=$b \n");