Introduction to Perl

Overview
Perl has been described as a kind of "Swiss Army Knife" of Unix like tools and utilities combined in a scripting language. The purpose of this course is to provide a gentle yet thorough introduction to the language of Perl, and an overview of some of the most useful and commonly encountered Perl modules.
All the Perl programming constructs are carefully explained, and a considerable amount of time will be devoted to the difficulat topics such as regular expressions and hashes. Although examples of using Perl modules for Web development and for system administration will be included in the course, these topics are dealt with in depth in more specialised courses.

Key Skills

• Ability to use scalars, arrays and hashes effectively
• Understanding of modular programming techniques in Perl - based on developing appropriate data structures and the algorithms to manipulate these data structures
• Confidence in using regular expressions to tackle information retrieval, data transformation and document processing tasks
• Writing Perl scripts for file system administration
• Ability to read and modify Perl system administration scripts
• Practical introduction to the Perl CGI module

Practical Work
The course will contain many exercises to develop and reinforce the concepts and techniques taught. Towards the end of the course the exercises will be built around an information retrieval and reporting task based on processing log files.

• Retrieving lines from a file containing particular patterns
• Using hashes to collect and organised statistical information about the types of events recorded in a log file
• Formatting the output of a report as a web page
• Implement a file backup and recovery application
• Use the values entered on a form to generate a customer reply letter

Course Contents
The Philosophy and Style of Perl

• Advantages of working with an interpreted language
• Perl's heritage in Unix
• Perl's extensibility
• Large number of Perl modules available for Perl

Perl Syntax and style

• Filehandles for basic Input/Output
• Statements and declarations
• Overview of Perl's data types

Scalars

• scalar values
• string literals
• metacharacters and quotation in string literals
• "Here" documents
• special literals
• variables and literals

Operators

• arithmetic operators
• string operators
• assignment operators
• autoincrement and autodecrement operators
• logical operators
• comparison operators

Control structures

• truth and falsity in Perl
• if -- elsif -- else statements
• SWITCH statements
• while loops and until loops
• for loops and foreach loops
• breaking out of loops with next and last

Regular expressions Arrays, Hashes, Typeglobs and Context

• arrays and list values
• associative arrays (hashes)
• scalar and list contexts
• void context
• interpolative context
• typeglobs and filehandles

Input operators

• backquote operator (command input)
• angle operator (line input)
• filename globbing operator

Regular expressions and pattern matching - advanced treatment

• rules or regexp pattern matching
• regular expression extensions
• pattern-matching operators

Scope rules

• global declarations
• scoped declarations

Subroutines

• passing arguments
• returning values
• localising variables using my and local
• passing symbol table entries (typeglobs)
• passing references
• prototypes

Generating formatted output

• using the printf subroutine
• using format and write

Perl special variables - an overview

• filehandle special variables
• regular expression special variables
• global special variables
• global special arrays

Perl's built in functions for

• manipulating scalars
• regular expressions and pattern matching
• numeric function computation
• array processing
• list processing
• hash processing
• input / output
• processing fixed length data and records
• working with filehandles, files and directories
• controlling flow of a script
• scoping
• performing system/process level tasks
• constructing and using modules
• constructing classes and objects
• interprocess communication
• obtaining user and group information
• obtaining network information
• socket programming
• time handling

Advanced topics

• references and nested data structures
• references and objects
• packages, modules and object classes
• working with the Standard Perl library
• debugging Perl scripts