print "main start\n";
&mySub(4);
print "main end\n";

sub mySub
{
     my ($oldValue, $callDepth, @leftOvers) = @_;
     if (!defined $oldValue) { $oldValue = 0; }
     if (!defined $callDepth) { $callDepth = 0; }

     # Increment call depth each time we get into mySub()
     $callDepth++;
     my $indentSize = $callDepth * 2;
     my $indentSpaces = sprintf("%${indentSize}s", "");

     # Show we've arrived -- indent according to call depth
     print "${indentSpaces}mySub($oldValue) BEGIN\n";

     # Cut value in half and recurse until zero
     my $newValue = int($oldValue / 2);
     if ($newValue > 0)
     {
          &mySub($newValue, $callDepth);
     }

     # Show we've returned -- indent according to call depth
     print "${indentSpaces}mySub($oldValue) END\n";

     # Bye-bye
     return;
}