Remember basic arithmetic from school? These work just
    like those.
   
Table 15-2. Arithmetic Operators
| Example | Name | Result | 
|---|
| -$a | Negation | Opposite of $a. | 
| $a + $b | Addition | Sum of $a and $b. | 
| $a - $b | Subtraction | Difference of $a and $b. | 
| $a * $b | Multiplication | Product of $a and $b. | 
| $a / $b | Division | Quotient of $a and $b. | 
| $a % $b | Modulus | Remainder of $a divided by $b. | 
    The division operator ("/") returns a float value anytime,
    even if the two operands are integers (or strings that get
    converted to integers).
   
Note: 
     Remainder $a % $b is negative for negative
     $a.
    
    See also the manual page on 
    Math functions.