What Is Scalar Data?
Perl's Built-in Warnings
Output with print
The if Control Structure
Getting User Input
The chomp Operator
The while Control Structure
The undef Value
The defined Function
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.
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 or the Gettysburg Address). Although you may think of numbers and strings as very different things, Perl uses them nearly interchangeably.
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.
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