book

Beginning Perl

by Curtis Ovid Poe

September 2012

Beginner

744 pages

15h 48m

English

Wrox

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Perl TodayGetting PerlThe Perl CommunityUsing perldocUsing a Terminal WindowCreating Hello, World!Summary
CPAN and METACPANCPAN ClientsSummary
What is Programming?A Few Things to Note Before Getting StartedScalarsArraysHashesSlicesContextScopeStrict, Warnings, and DiagnosticsPerl’s Built-in VariablesSummary
Using ScalarsArray and List FunctionsBuilt-in Hash FunctionsScoping KeywordsSummary
Using the if Statementfor/foreach loopsUsing while/until LoopsStatement Modifiersgiven/whenSummary
References 101Working with ReferencesSummary
Subroutine SyntaxReturning DataFAIL!Subroutine ReferencesPrototypesRecursionThings to Watch ForSummary

Basic MatchingAdvanced MatchingCommon Regular Expression IssuesSummary
Basic File HandlingDirectoriesUnicodeUseful ModulesSummary
Basic Sortingmap and grepPutting It All TogetherSummary
Namespaces and PackagesSubroutines in Other PackagesBEGIN, UNITCHECK, CHECK, INIT, and ENDPlain Old Documentation (POD)Creating and Installing ModulesSummary
What Are Objects? The Ævar the Personal ShopperThree Rules of Perl OOObjects – Another ViewA Brief RecapGotchasSummary
Understanding Basic Moose SyntaxAdvanced Moose SyntaxMoose Best PracticesSummary
Basic TestsUnderstanding Test::More Test FunctionsUsing Other Testing ModulesUnderstanding xUnit Style Using TestingSummary
A Brief Introduction to HTTPWeb ClientsSummary
Using the DBISelecting Basic DataSummary
The Command LineOther ProgramsSummary
Using CSV DataUnderstanding Basic XMLHandling DatesUnderstanding Your ProgramSummary
What Next?Understanding Object-Relational MappersUsing the Template ToolkitUsing Catalyst to Build AppsSummary

Content preview from Beginning Perl

Chapter 5 Control Flow

WHAT YOU WILL LEARN IN THIS CHAPTER:

Working with if/elsif/else expressions
What are and when to use for/foreach loops
Understanding and working with while/until loops
Understanding the various statement modifiers and how to use do while/do until
What are given/when statements and statement modifiers and when to use them

WROX.COM CODE DOWNLOADS FOR THIS CHAPTER

The wrox.com code downloads for this chapter are found at http://www.wrox.com/WileyCDA/WroxTitle/Beginning-Perl.productCd-1118013847,descCd-DOWNLOAD.html on the Download Code tab. The code for this chapter is divided into the following major examples:

Example_5_1_unique.pl
Example_5_2_arrays.pl

From previous chapters, you now understand some of the basics of Perl, but now you get closer to the heart of programming. When you program, you constantly make decisions loop over data based on those decisions. That’s what this chapter is all about: how Perl makes decisions and looping over data.

USING THE IF STATEMENT

This section starts with boolean logic. As explained in Chapter 4, the following values are considered “false” in Perl:

undef
"" (the empty string)
0
0.0
"0" (the “string” zero)

Some languages have specific boolean objects, or TRUE and FALSE identifiers. Perl does things a little differently. As you work through the examples, try to see what Perl does and why. If you have experience with programming languages that have a different approach, consider the strengths and weaknesses of the different ...