Learning Perl, 6th Edition

Chapter 2. Scalar Data

In English, as in many other spoken languages, you’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.^[29] 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^[30] or the Gettysburg Address). Although you may think of numbers and strings as very different things, Perl uses them nearly interchangeably.

You can act on a scalar value with operators (like addition or concatenation), generally yielding a scalar result. You can store a scalar value in a scalar variable. You can read scalars from files and devices, and write to them 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 Have the Same Format Internally

As you’ll see in the next few paragraphs, you can specify both integers (whole numbers, like 255 or 2,001) and floating-point numbers (real numbers with decimal points, like 3.14159, or 1.35 × 1,025). But internally, Perl computes with double-precision floating-point values.^[31] 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.^[32] You probably won’t notice the ...