Programming Perl, 4th Edition

Chapter 8. References

For both practical and philosophical reasons, Perl has always been biased in favor of flat, linear data structures. And for many problems, this is just what you want.

Suppose you wanted to build a simple table (two-dimensional array) showing vital statistics—age, eye color, and weight—for a group of people. You could do this by first creating an array for each individual:

@john = (47, "brown", 186);
@mary = (23, "hazel", 128);
@bill = (35, "blue",  157);

You could then construct a single, additional array consisting of the names of the other arrays:

@vitals = ("john", "mary", "bill");

To change John’s eyes to “red” after a night on the town, we want a way to change the contents of the @john array given only the simple string “john”. This is the basic problem of indirection, which various languages solve in various ways. In C, the most common form of indirection is the pointer, which lets one variable hold the memory address of another variable. In Perl, the most common form of indirection is the reference.