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<chapter id="intermediateperl-CHP-1">
    <title>Introduction</title>

    <para>Welcome to the next step in your understanding of Perl. You’re
    probably here either because you want to learn to write programs that are
    more than 100 lines long or because your boss has told you to do
    so.</para>

    <para>See, our <emphasis>Learning Perl</emphasis> book was great because
    it introduced the use of Perl for short and medium programs (which is most
    of the programming done in Perl, we’ve observed). But, to avoid having
    “the Llama book” be big and intimidating, we left a lot of information
    out, deliberately and carefully.</para>

    <para>In the pages that follow, you can get “the rest of the story” in the
    same style as our friendly Llama book. It covers what you need to write
    programs that are 100 to 10,000 lines long.</para>

    <para>For example, you’ll learn how to work with multiple programmers on
    the same project. This is great, because unless you work 35 hours each
    day, you’ll need some help with larger tasks. You’ll also need to ensure
    that all your code fits with the other code as you develop it for the
    final application.</para>

    <para>This book will also show you how to deal with larger and more
    complex data structures<indexterm class="singular" id="IDX-CHP-1-0009" significance="normal">
        <primary>complex data structures</primary>
      </indexterm> , such as what we might casually call a “hash of hashes” or
    an “array of arrays of hashes of arrays.” Once you know a little about
    references, you’re on your way to arbitrarily complex data
    structures.</para>

    <para>And then there’s the buzzworthy notion of object-oriented
    programming (OOP), which allows parts of your code (or hopefully code from
    others) to be reused with minor or major variations within the same
    program. The book will cover that as well, even if you’ve never seen
    objects before.</para>

    <para>An important aspect of working in teams is having a release
    cycle<indexterm class="singular" id="IDX-CHP-1-0010" significance="normal">
        <primary>release cycle</primary>
      </indexterm> and tests for unit and integration testing<indexterm class="singular" id="IDX-CHP-1-0011" significance="normal">
        <primary>testing</primary>
      </indexterm> . You’ll learn the basics of packaging your code as a
    distribution and providing unit tests for that distribution, both for
    development and for verifying that your code works in the ultimate end
    environment.</para>

    <para>And, just as was promised and delivered in <emphasis>Learning
    Perl</emphasis>, we’ll entertain you along the way with interesting
    examples and bad puns. (We’ve sent Fred, Barney, Betty, and Wilma home,
    though. A new cast of characters will take the starring roles.)</para>

    <sect1 id="intermediateperl-CHP-1-SECT-1">
      <title>What Should You Know Already?</title>

      <para><indexterm class="singular" id="IDX-CHP-1-0012" significance="normal">
          <primary>exercises</primary>

          <secondary>using</secondary>
        </indexterm>We’ll presume that you’ve already read <emphasis>Learning
      Perl</emphasis>, or at least pretend you have, and that you’ve played
      enough with Perl to already have those basics down. For example, you
      won’t see an explanation in this book that shows how to access the
      elements of an array or return a value from a subroutine.</para>

      <para>Make sure you know the following things:</para>

      <itemizedlist>
        <listitem>
          <para>How to run a Perl program on your system</para>
        </listitem>

        <listitem>
          <para>The three basic Perl variable types: scalars, arrays, and
          hashes</para>
        </listitem>

        <listitem>
          <para>Control structures such as <literal moreinfo="none">while</literal>, <literal moreinfo="none">if</literal>, <literal moreinfo="none">for</literal>, and <literal moreinfo="none">foreach</literal></para>
        </listitem>

        <listitem>
          <para>Subroutines</para>
        </listitem>

        <listitem>
          <para>Perl operators such as <literal moreinfo="none">grep</literal>, <literal moreinfo="none">map</literal>, <literal moreinfo="none">sort</literal>, and <literal moreinfo="none">print</literal></para>
        </listitem>

        <listitem>
          <para>File manipulation such as <literal moreinfo="none">open</literal>, file reading, and <literal moreinfo="none">-X</literal> (file tests)</para>
        </listitem>
      </itemizedlist>

      <para>You might pick up deeper insight into these topics in this book,
      but we’re going to presume you know the basics.</para>
    </sect1>

    <sect1 id="intermediateperl-CHP-1-SECT-2">
      <title>What About All Those Footnotes?</title>

      <para>Like <emphasis>Learning Perl</emphasis>, this book relegates some
      of the more esoteric items out of the way for the first reading and
      places those items in footnotes.<footnote id="intermediateperl-CHP-1-FN1">
          <para>Like this.</para>
        </footnote> You should skip those the first time through and pick them
      up on a rereading. You will not find anything in a footnote that you’ll
      need to understand any of the material we present later.</para>
    </sect1>

    <sect1 id="intermediateperl-CHP-1-SECT-3">
      <title>What’s with the Exercises?</title>

      <para>Hands-on training gets the job done better. The best way to
      provide this training is with a series of exercises after every
      half-hour to hour of presentation. Of course, if you’re a speed reader,
      the end of the chapter may come a bit sooner than a half hour. Slow
      down, take a breather, and do the exercises!</para>

      <para>Each exercise has a “minutes to complete” rating. We intend for
      this rating to hit the midpoint of the bell curve, but don’t feel bad if
      you take significantly longer or shorter. Sometimes it’s just a matter
      of how many times you’ve faced similar programming tasks in your studies
      or jobs. Use the numbers merely as a guideline.</para>

      <para>Every exercise has its answer in the Appendix. Again, try not to
      peek; you’ll ruin the value of the exercise.</para>
    </sect1>

    <sect1 id="intermediateperl-CHP-1-SECT-4">
      <title>What If I’m a Perl Course Instructor?</title>

      <para>If you’re a Perl instructor who has decided to use this as your
      textbook, you should know that each set of exercises is short enough for
      most students to complete in 45 minutes to an hour, with a little time
      left over for a break. Some chapters’ exercises should be quicker, and
      some may take longer. That’s because once all those little numbers in
      square brackets were written, we discovered that we didn’t know how to
      add.</para>

      <para>So let’s get started. Class begins after you turn the page . . .
      .</para>
    </sect1>
  </chapter>