Chapter 2. Scalar Data

2.1. 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.[40]

[40]This has little to do with the similar term from mathematics or physics in that a scalar is a single thing; there are no "vectors" in Perl.

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[41] or the Gettysburg Address). Although you may think of numbers and strings as very different things, Perl uses them nearly interchangeably.

[41]If you have been using other programming languages, you may think of hello as a collection of five characters, rather than as a single thing. But in Perl, a string is a single scalar value. Of course, we can access the individual characters when we need to; we'll see how to do that in later chapters.

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.