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Contents:
What Is Scalar Data?
Numbers
Strings
Automatic Conversion Between Numbers and Strings
Scalar Variables
Interpolation of Scalar Variables into Strings
Scalar Operators
Scalar Functions
<STDIN> as a Scalar Value
Output with print
The Undefined Value
The defined Function
Exercises
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.[ 1]
A scalar is the simplest kind of data that Perl manipulates. A scalar is
either a number (like 4 or 3.25e20) or a string of characters (like hello[
2] or the Gettysburg Address). Although you may think of
numbers and strings as very different things, Perl uses them nearly interchangeably, so we'll
describe them together.
A scalar value can be acted upon with operators (like plus 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 written out as well.
Next: Numbers
[1]
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.
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[2]
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 lessons.
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