2.3;   # Evaluation
$Foo = $a + 2.0;   # Assignment
</pre></div>

<p>
To provide such access, variables are commonly manipulated using a
pair of get/set functions.  For example, whenever the value of a
variable is read, a "get" function is invoked.  Similarly, whenever
the value of a variable is changed, a "set" function is called.
</p>

<p>
In many languages, calls to the get/set functions can be attached to
evaluation and assignment operators.  Therefore, evaluating a variable
such as <tt>$Foo</tt> might 