Learning Perl, 5th Edition

Chapter 3. Lists and Arrays

If a scalar is the “singular” in Perl, as we described it at the beginning of Chapter 2, the “plural” in Perl is represented by lists and arrays.

A list is an ordered collection of scalars. An array is a variable that contains a list. In Perl, the two terms are often used as if they’re interchangeable. But, to be accurate, the list is the data, and the array is the variable. You can have a list value that isn’t in an array, but every array variable holds a list (although that list may be empty). Figure 3-1 represents a list, whether it’s stored in an array or not.

Figure 3-1. A list with five elements

Each element of an array or list is a separate scalar variable with an independent scalar value. These values are ordered—that is, they have a particular sequence from the first to the last element. The elements of an array or list are indexed by small integers starting at zero^[9] and counting by ones, so the first element of any array or list is always element zero.

Since each element is an independent scalar value, a list or array may hold numbers, strings, undef values, or any mixture of different scalar values. Nevertheless, it’s most common to have all elements of the same type, such as a list of book titles (all strings) or a list of cosines (all numbers).

Arrays and lists can have any number of elements. The smallest one has no elements, while the largest ...