The Perl Cookbook is a comprehensive collection of problems, solutions, and practical examples for anyone programming in Perl. Topics range from beginner questions to techniques that even the most experienced of Perl programmers will learn from. More than just a collection of tips and tricks, the Perl Cookbook is the long-awaited companion volume to Programming Perl, filled with previously unpublished Perl arcana.

The Perl Cookbook contains thousands upon thousands of examples ranging from brief one-liners to complete applications. Covered topic areas spread across nearly four hundred separate "recipes," including:

• Manipulation of strings, numbers, dates, arrays, and hashes
• Reading, writing, and updating text and binary files
• Pattern matching and text substitutions
• Subroutines, libraries, and modules
• References, data structures, objects, and classes
• Signals and exceptions
• Accessing text, hashes, and SQL databases
• Screen addressing, menus, and graphical applications
• Managing other processes
• Writing secure scripts
• Client-server programming
• Internet applications programming with mail, news, ftp, and telnet
• CGI programming and Web automation

These recipes were rigorously reviewed by scores of the best minds inside and outside Perl, foremost of which was Larry Wall, the creator of Perl himself.

The Perl Cookbook is written by Tom Christiansen, Perl evangelist and coauthor of the bestselling Programming Perl and Learning Perl; and Nathan Torkington, Perl trainer and co-maintainer of the Perl Frequently Asked Questions list.

You'll find recipes for manipulating strings, numbers, dates, arrays, and hashes; pattern matching and text substitutions; references, data structures, objects, and classes; signals and exceptions; accessing text, hashes, and SQL databases; and managing other processes. You'll also uncover recipes for writing secure scripts; client-server programming; Internet applications programming with mail, news, ftp, and telnet; and CGI programming and Web automation.

 Table of Contents
Foreword  

Preface 

1. Strings 
1.0. Introduction
      1.1. Accessing Substrings 
      1.2. Establishing a Default Value 
      1.3. Exchanging Values Without Using Temporary Variables 
      1.4. Converting Between ASCII Characters and Values 
      1.5. Processing a String One Character at a Time 
      1.6. Reversing a String by Word or Character 
      1.7. Expanding and Compressing Tabs 
      1.8. Expanding Variables in User Input 
      1.9. Controlling Case 
      1.10. Interpolating Functions and Expressions Within Strings 
      1.11. Indenting Here Documents 
      1.12. Reformatting Paragraphs 
      1.13. Escaping Characters 
      1.14. Trimming Blanks from the Ends of a String 
      1.15. Parsing Comma-Separated Data 
      1.16. Soundex Matching 
      1.17. Program: fixstyle 
      1.18. Program: psgrep 
2. Numbers 
2.0. Introduction
      2.1. Checking Whether a String Is a Valid Number 
      2.2. Comparing Floating-Point Numbers 
      2.3. Rounding Floating-Point Numbers 
      2.4. Converting Between Binary and Decimal 
      2.5. Operating on a Series of Integers 
      2.6. Working with Roman Numerals 
      2.7. Generating Random Numbers 
      2.8. Generating Different Random Numbers 
      2.9. Making Numbers Even More Random 
      2.10. Generating Biased Random Numbers 
      2.11. Doing Trigonometry in Degrees, not Radians 
      2.12. Calculating More Trigonometric Functions 
      2.13. Taking Logarithms 
      2.14. Multiplying Matrices 
      2.15. Using Complex Numbers 
      2.16. Converting Between Octal and Hexadecimal 
      2.17. Putting Commas in Numbers 
      2.18. Printing Correct Plurals 
      2.19. Program: Calculating Prime Factors 
3. Dates and Times 
3.0. Introduction
      3.1. Finding Today's Date 
      3.2. Converting DMYHMS to Epoch Seconds 
      3.3. Converting Epoch Seconds to DMYHMS 
      3.4. Adding to or Subtracting from a Date 
      3.5. Difference of Two Dates 
      3.6. Day in a Week/Month/Year or Week Number 
      3.7. Parsing Dates and Times from Strings 
      3.8. Printing a Date 
      3.9. High-Resolution Timers 
      3.10. Short Sleeps 
      3.11. Program: hopdelta 
4. Arrays 
4.0. Introduction
      4.1. Specifying a List In Your Program 
      4.2. Printing a List with Commas 
      4.3. Changing Array Size 
      4.4. Doing Something with Every Element in a List 
      4.5. Iterating Over an Array by Reference 
      4.6. Extracting Unique Elements from a List 
      4.7. Finding Elements in One Array but Not Another 
      4.8. Computing Union, Intersection, or Difference of Unique Lists 
      4.9. Appending One Array to Another 
      4.10. Reversing an Array 
      4.11. Processing Multiple Elements of an Array 
      4.12. Finding the First List Element That Passes a Test 
      4.13. Finding All Elements in an Array Matching Certain Criteria 
      4.14. Sorting an Array Numerically 
      4.15. Sorting a List by Computable Field 
      4.16. Implementing a Circular List 
      4.17. Randomizing an Array 
      4.18. Program: words 
      4.19. Program: permute 
5. Hashes 
5.0. Introduction
      5.1. Adding an Element to a Hash 
      5.2. Testing for the Presence of a Key in a Hash 
      5.3. Deleting from a Hash 
      5.4. Traversing a Hash 
      5.5. Printing a Hash 
      5.6. Retrieving from a Hash in Insertion Order 
      5.7. Hashes with Multiple Values Per Key 
      5.8. Inverting a Hash 
      5.9. Sorting a Hash 
      5.10. Merging Hashes 
      5.11. Finding Common or Different Keys in Two Hashes 
      5.12. Hashing References 
      5.13. Presizing a Hash 
      5.14. Finding the Most Common Anything 
      5.15. Representing Relationships Between Data 
      5.16. Program: dutree 
6. Pattern Matching 
6.0. Introduction
      6.1. Copying and Substituting Simultaneously 
      6.2. Matching Letters 
      6.3. Matching Words 
      6.4.  Commenting Regular Expressions 
      6.5. Finding the Nth Occurrence of a Match 
      6.6. Matching Multiple Lines 
      6.7. Reading Records with a Pattern Separator 
      6.8. Extracting a Range of Lines 
      6.9. Matching Shell Globs as Regular Expressions 
      6.10. Speeding Up Interpolated Matches 
      6.11. Testing for a Valid Pattern 
      6.12. Honoring Locale Settings in Regular Expressions 
      6.13. Approximate Matching 
      6.14. Matching from Where the Last Pattern Left Off 
      6.15. Greedy and Non-Greedy Matches 
      6.16. Detecting Duplicate Words 
      6.17. Expressing AND, OR, and NOT in a Single Pattern 
      6.18. Matching Multiple-Byte Characters 
      6.19. Matching a Valid Mail Address 
      6.20. Matching Abbreviations 
      6.21. Program: urlify 
      6.22. Program: tcgrep 
      6.23. Regular Expression Grabbag 
7. File Access 
7.0. Introduction
      7.1. Opening a File 
      7.2. Opening Files with Unusual Filenames 
      7.3. Expanding Tildes in Filenames 
      7.4. Making Perl Report Filenames in Errors 
      7.5. Creating Temporary Files 
      7.6. Storing Files Inside Your Program Text 
      7.7. Writing a Filter 
      7.8. Modifying a File in Place with Temporary File 
      7.9. Modifying a File in Place with -i Switch 
      7.10. Modifying a File in Place Without a Temporary File 
      7.11. Locking a File 
      7.12. Flushing Output 
      7.13. Reading from Many Filehandles Without Blocking 
      7.14. Doing Non-Blocking I/O 
      7.15. Bytes to Read
      7.16. Storing Filehandles in Variables 
      7.17. Caching Open Output Filehandles 
      7.18. Printing to Many Filehandles Simultaneously 
      7.19. Opening and Closing File Descriptors by Number 
      7.20. Copying Filehandles 
      7.21. Program: netlock 
      7.22. Program: lockarea 
8. File Contents 
8.0. Introduction
      8.1. Reading Lines with Continuation Characters 
      8.2. Counting Lines (or Paragraphs or Records) in a File 
      8.3. Processing Every Word in a File 
      8.4. Reading a File Backwards by Line or Paragraph 
      8.5. Trailing a Growing File 
      8.6. Picking a Random Line from a File 
      8.7. Randomizing All Lines 
      8.8. Reading a Particular Line in a File 
      8.9. Processing Variable-Length Text Fields 
      8.10. Removing the Last Line of a File 
      8.11. Processing Binary Files 
      8.12. Using Random-Access I/O 
      8.13. Updating a Random-Access File 
      8.14. Reading a String from a Binary File 
      8.15. Reading Fixed-Length Records 
      8.16. Reading Configuration Files 
      8.17. Testing a File for Trustworthiness 
      8.18. Program: tailwtmp 
      8.19. Program: tctee 
      8.20. Program: laston 
9. Directories 
9.0. Introduction
      9.1. Getting and Setting Timestamps 
      9.2. Deleting a File 
      9.3. Copying or Moving a File 
      9.4. Recognizing Two Names for the Same File 
      9.5. Processing All Files in a Directory 
      9.6. Globbing, or Getting a List of Filenames Matching a Pattern 
      9.7. Processing All Files in a Directory Recursively 
      9.8. Removing a Directory and Its Contents 
      9.9. Renaming Files 
      9.10. Splitting a Filename into Its Component Parts 
      9.11. Program: symlink 
      9.12. Program: lst 
10. Subroutines 
10.0. Introduction
      10.1. Accessing Subroutine Arguments 
      10.2. Making Variables Private to a Function 
      10.3. Creating Persistent Private Variables 
      10.4. Determining Current Function Name 
      10.5. Passing Arrays and Hashes by Reference 
      10.6. Detecting Return Context 
      10.7. Passing by Named Parameter 
      10.8. Skipping Selected Return Values 
      10.9. Returning More Than One Array or Hash 
      10.10. Returning Failure 
      10.11. Prototyping Functions 
      10.12. Handling Exceptions 
      10.13. Saving Global Values 
      10.14. Redifining a Function 
      10.15. Trapping Undefined Function Calls with AUTOLOAD 
      10.16. Nesting Subroutines 
      10.17. Program: Sorting Your Mail 
11. References and Records 
11.0. Introduction
      11.1. Taking References to Arrays 
      11.2. Making Hashes of Arrays 
      11.3. Taking References to Hashes 
      11.4. Taking References to Functions 
      11.5. Taking References to Scalars 
      11.6. Creating Arrays of Scalar References 
      11.7. Using Closures Instead of Objects 
      11.8. Creating References to Methods 
      11.9. Constructing Records 
      11.10. Reading and Writing Hash Records to Text Files 
      11.11. Printing Data Structures 
      11.12. Copying Data Structures 
      11.13. Storing Data Structures to Disk 
      11.14. Transparently Persistent Data Structures 
      11.15. Program: Binary Trees 
12. Packages, Libraries, and Modules 
12.0. Introduction
      12.1. Defining a Module's Interface 
      12.2. Trapping Errors in require or use 
      12.3. Delaying use Until Run Time 
      12.4. Making Variables Private to a Module 
      12.5. Determining the Caller's Package 
      12.6. Automating Module Clean-Up 
      12.7. Keeping Your Own Module Directory 
      12.8. Preparing a Module for Distribution 
      12.9. Speeding Module Loading with SelfLoader 
      12.10. Speeding Up Module Loading with Autoloader 
      12.11. Overriding Built-In Functions 
      12.12. Reporting Errors and Warnings Like Built-Ins 
      12.13. Referring to Packages Indirectly 
      12.14. Using h2ph to Translate C #include Files 
      12.15. Using h2xs to Make a Module with C Code 
      12.16. Documenting Your Module with Pod 
      12.17. Building and Installing a CPAN Module 
      12.18. Example: Module Template 
      12.19. Program: Finding Versions and Descriptions of Installed Modules 
13. Classes, Objects, and Ties 
13.0. Introduction
      13.1. Constructing an Object 
      13.2. Destroying an Object 
      13.3. Managing Instance Data 
      13.4. Managing Class Data 
      13.5. Using Classes as Structs 
      13.6. Cloning Objects 
      13.7. Calling Methods Indirectly 
      13.8. Determining Subclass Membership 
      13.9. Writing an Inheritable Class 
      13.10. Accessing Overridden Methods 
      13.11. Generating Attribute Methods Using AUTOLOAD 
      13.12. Solving the Data Inheritance Problem 
      13.13. Coping with Circular Data Structures 
      13.14. Overloading Operators 
      13.15. Creating Magic Variables with tie 
14. Database Access 
14.0. Introduction
      14.1. Making and Using a DBM File 
      14.2. Emptying a DBM File 
      14.3. Converting Between DBM Files 
      14.4. Merging DBM Files 
      14.5. Locking DBM Files 
      14.6. Sorting Large DBM Files 
      14.7. Treating a Text File as a Database Array 
      14.8. Storing Complex Data in a DBM File 
      14.9. Persistent Data 
      14.10. Executing an SQL Command Using DBI and DBD 
      14.11. Program: ggh-Grep Netscape Global History 
15. User Interfaces 
15.0. Introduction
      15.1. Parsing Program Arguments 
      15.2. Testing Whether a Program Is Running Interactively 
      15.3. Clearing the Screen 
      15.4. Determining Terminal or Window Size 
      15.5. Changing Text Color 
      15.6. Reading from the Keyboard 
      15.7. Ringing the Terminal Bell 
      15.8. Using POSIX termios 
      15.9. Checking for Waiting Input 
      15.10. Reading Passwords 
      15.11. Editing Input 
      15.12. Managing the Screen 
      15.13. Controlling Another Program with Expect 
      15.14. Creating Menus with Tk 
      15.15. Creating Dialog Boxes with Tk 
      15.16. Responding to Tk Resize Events 
      15.17. Removing the DOS Shell Window with Windows Perl/Tk 
      15.18. Program: Small termcap program 
      15.19. Program: tkshufflepod 
16. Process Management and Communication 
16.0. Introduction
      16.1. Gathering Output from a Program 
      16.2. Running Another Program 
      16.3. Replacing the Current Program with a Different One 
      16.4. Reading or Writing to Another Program 
      16.5. Filtering Your Own Output 
      16.6. Preprocessing Input 
      16.7. Reading STDERR from a Program 
      16.8. Controlling Input and Output of Another Program 
      16.9. Controlling the Input, Output, and Error of Another Program 
      16.10. Communicating Between Related Processes 
      16.11. Making a Process Look Like a File with Named Pipes 
      16.12. Sharing Variables in Different Processes 
      16.13. Listing Available Signals 
      16.14. Sending a Signal 
      16.15. Installing a Signal Handler 
      16.16. Temporarily Overriding a Signal Handler 
      16.17. Writing a Signal Handler 
      16.18. Catching Ctrl-C 
      16.19. Avoiding Zombie Processes 
      16.20. Blocking Signals 
      16.21. Timing Out an Operation 
      16.22. Program: sigrand 
17. Sockets 
17.0. Introduction
      17.1. Writing a TCP Client 
      17.2. Writing a TCP Server 
      17.3. Communicating over TCP 
      17.4. Setting Up a UDP Client 
      17.5. Setting Up a UDP Server 
      17.6. Using UNIX Domain Sockets 
      17.7. Identifying the Other End of a Socket 
      17.8. Finding Your Own Name and Address 
      17.9. Closing a Socket After Forking 
      17.10. Writing Bidirectional Clients 
      17.11. Forking Servers 
      17.12. Pre-Forking Servers 
      17.13. Non-Forking Servers 
      17.14. Writing a Multi-Homed Server 
      17.15. Making a Daemon Server 
      17.16. Restarting a Server on Demand 
      17.17. Program: backsniff 
      17.18. Program: fwdport 
18. Internet Services 
18.0. Introduction
      18.1. Simple DNS Lookups 
      18.2. Being an FTP Client 
      18.3. Sending Mail 
      18.4. Reading and Posting Usenet News Messages 
      18.5. Reading Mail with POP3 
      18.6. Simulating Telnet from a Program 
      18.7. Pinging a Machine 
      18.8. Using Whois to Retrieve Information from the InterNIC 
      18.9. Program: expn and vrfy 
19. CGI Programming 
19.0. Introduction
      19.1. Writing a CGI Script 
      19.2. Redirecting Error Messages 
      19.3. Fixing a 500 Server Error 
      19.4. Writing a Safe CGI Program 
      19.5. Making CGI Scripts Efficient 
      19.6. Executing Commands Without Shell Escapes 
      19.7. Formatting Lists and Tables with HTML Shortcuts 
      19.8. Redirecting to a Different Location 
      19.9. Debugging the Raw HTTP Exchange 
      19.10. Managing Cookies 
      19.11. Creating Sticky Widgets 
      19.12. Writing a Multiscreen CGI Script 
      19.13. Saving a Form to a File or Mail Pipe 
      19.14. Program: chemiserie 
20. Web Automation 
20.0. Introduction
      20.1. Fetching a URL from a Perl Script 
      20.2. Automating Form Submission 
      20.3. Extracting URLs 
      20.4. Converting ASCII to HTML 
      20.5. Converting HTML to ASCII 
      20.6. Extracting or Removing HTML Tags 
      20.7. Finding Stale Links 
      20.8. Finding Fresh Links 
      20.9. Creating HTML Templates 
      20.10. Mirroring Web Pages 
      20.11. Creating a Robot 
      20.12. Parsing a Web Server Log File 
      20.13. Processing Server Logs 
      20.14. Program: htmlsub 
      20.15. Program: hrefsub 

Index