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
 or the Gettysburg Address). Though you may think of numbers and strings as different things, Perl uses them nearly interchangeably.
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.
Though 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.
As you’ll see in the next few paragraphs, you can specify integers (whole numbers, like 255 or 2001) and floating-point numbers (real numbers with decimal points, like 3.14159, or 1.35×1025). But internally, Perl computes with double-precision floating-point values. 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. You probably won’t notice the conversion ...