my $i = 0;  

print ++$i + 1,"  I: $i\n";           # guess 2
print $i++ + 1,"  I: $i\n";           # guess 2
print $i + $i++,"  I: $i\n";          # guess 4
print ++$i + ++$i," I: $i\n";         # guess 9
print ++$i + $i++ + 1," I: $i\n";     # guess 12