Learning Perl, 3rd Edition

Chapter 2. Scalar Data

What Is Scalar Data?

In English, as in many other spoken languages, we’re used to distinguishing between singular and plural. As a computer language designed by a human linguist, Perl is similar. As a general rule, when Perl has just one of something, that’s a scalar.^[1]

A scalar is the simplest kind of data that Perl manipulates. Most scalars are either a number (like 255 or 3.25e20) or a string of characters (like hello ^[2] or the Gettysburg Address). Although you may think of numbers and strings as very different things, Perl uses them nearly interchangeably.

A scalar value can be acted upon with operators (like addition or concatenate), generally yielding a scalar result. A scalar value can be stored into a scalar variable. Scalars can be read from files and devices, and can be written out as well.

Numbers

Although a scalar is most often either a number or a string, it’s useful to look at numbers and strings separately for the moment. We’ll cover numbers first, and then move on to strings.

All Numbers Are the Same Format Internally

As you’ll see in the next few paragraphs, you can specify both integers (whole numbers, like 255 or 2001) and floating-point numbers (real numbers with decimal points, like 3.14159, or 1.35 x 1025). But internally, Perl computes with double-precision floating-point values.^[3] This means that there are no integer values internal to Perl—an integer constant in the program is treated as the equivalent floating-point value.^[4]