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31.16. use overload
In the Number module:
package Number;
use overload "+" => \&myadd,
"-" => \&mysub,
"*=" => "multiply_by";
In your program:
use Number;
$a = new Number 57;
$b = $a + 5;
The built-in operators work well on strings and numbers, but make
little sense when applied to object references (since, unlike C or C++,
Perl doesn''t allow pointer arithmetic). The overload pragma lets
you redefine the meanings of these built-in operations when applied to
objects of your own design. In the previous example, the call to the
pragma redefines three operations on Number objects: addition will
call the Number::myadd function, subtraction will call the
Number::mysub function, and the multiplicative assignment operator
will call the multiply_by method in class Number (or one of its base
classes). We say of these operators that they are now overloaded
because they have additional meanings overlaid on them (and not because
they have too many meanings--though that may also be the case).For much more on overloading, see Chapter 13, "Overloading".