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<h1 class="chapter">Chapter 2. Scalar Data</h1>
<div class="htmltoc"><h4 class="tochead">Contents:</h4>
<p> <a href="#lperl3-CHP-2-SECT-1">What Is Scalar Data?</a><br />
<a href="ch02_02.htm">Numbers</a><br />
<a href="ch02_03.htm">Strings</a><br />
<a href="ch02_04.htm">Perl's Built-in Warnings</a><br />
<a href="ch02_05.htm">Scalar Variables</a><br />
<a href="ch02_06.htm">Output with print </a><br />
<a href="ch02_07.htm">The if Control Structure</a><br />
<a href="ch02_08.htm">Getting User Input</a><br />
<a href="ch02_09.htm">The chomp Operator</a><br />
<a href="ch02_10.htm">The while Control Structure</a><br />
<a href="ch02_11.htm">The undef Value</a><br />
<a href="ch02_12.htm">The defined Function</a><br />
<a href="ch02_13.htm">Exercises</a><br /></p></div>
<div class="sect1"><a name="lperl3-CHP-2-SECT-1" /></a>
<h2 class="sect1">2.1. What Is Scalar Data?</h2>
<p><a name="INDEX-111" /></a>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
<em class="emphasis">scalar</em>.<a href="#FOOTNOTE-40">[40]</a>
</p><blockquote class="footnote"> <a name="FOOTNOTE-40" /></a><p>[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. </p>
</blockquote>
<p>A <em class="emphasis">scalar</em> 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 <tt class="literal">hello</tt><a href="#FOOTNOTE-41">[41]</a> or the Gettysburg Address). Although you may think of
numbers and strings as very different things, Perl uses them nearly
interchangeably.
</p><blockquote class="footnote">
<a name="FOOTNOTE-41" /></a><p>[41]If you have been using other programming languages, you may
think of <tt class="literal">hello</tt> 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.</p>
</blockquote>
<p>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.
</p>
</div>
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