Chapter 2.  Scalar Data

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

^[*] 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.

^[] 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, you can access the individual characters when you need to; you'll see how to do that in later chapters.

A scalar value can be acted on with operators (such as addition or concatenation), 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.