print $|++ for (0..9);  print"   post ++\n";
print $|-- for (0..9);  print"   post --\n";
print ++$| for (0..9);  print"   pre ++\n";
print --$| for (0..9);  print"   pre --\n";

##</code><code>##

0111111111   post ++
1010101010   post --
1111111111   pre ++
0101010101   pre --