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Programming Perl, 3rd Edition

by Larry Wall, Tom Christiansen, Jon Orwant

July 2000

Intermediate to advanced

1104 pages

35h 1m

English

O'Reilly Media, Inc.

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1.1. Getting Started
1.2.1. Variable Syntax1.2.1.1. Singularities1.2.1.2. Pluralities1.2.1.2.1. Arrays.1.2.1.2.2. Hashes.1.2.1.3. Complexities1.2.1.4. Simplicities1.2.2. Verbs
1.3.1. How to Do It
1.5.1. Some Binary Arithmetic Operators1.5.2. String Operators1.5.3. Assignment Operators1.5.4. Unary Arithmetic Operators1.5.5. Logical Operators1.5.6. Some Numeric and String Comparison Operators1.5.7. Some File Test Operators
1.6.1. What Is Truth?1.6.1.1. The if and unless statements1.6.2. Iterative (Looping) Constructs1.6.2.1. The while and until statements1.6.2.2. The for statement1.6.2.3. The foreach statement1.6.2.4. Breaking out: next and last
1.7.1. Quantifiers1.7.2. Minimal Matching1.7.3. Nailing Things Down1.7.4. Backreferences
2.1. Atoms
2.5.1. Name Lookups
2.6.1. Numeric Literals2.6.2. String Literals2.6.3. Pick Your Own Quotes2.6.4. Or Leave the Quotes Out Entirely2.6.5. Interpolating Array Values2.6.6. "Here" Documents2.6.7. V-String Literals2.6.8. Other Literal Tokens
2.7.1. Scalar and List Context2.7.2. Boolean Context2.7.3. Void Context2.7.4. Interpolative Context
2.8.1. List Assignment2.8.2. Array Length
2.11.1. Command Input (Backtick) Operator2.11.2. Line Input (Angle) Operator2.11.3. Filename Globbing Operator
3.1. Terms and List Operators (Leftward)
4.1. Simple Statements
4.4.1. while and until Statements4.4.2. for Loops4.4.3. foreach Loops4.4.4. Loop Control
4.5.1. Case Structures
4.8.1. Scoped Variable Declarations4.8.2. Lexically Scoped Variables: my4.8.3. Lexically Scoped Global Declarations: our4.8.4. Dynamically Scoped Variables: local
4.9.1. Controlling Warnings4.9.2. Controlling the Use of Globals
5.1. The Regular Expression Bestiary
5.2.1. Pattern Modifiers5.2.2. The m// Operator (Matching)5.2.3. The s/// Operator (Substitution)5.2.3.1. Modifying strings en passant5.2.3.2. When a global substitution just isn't global enough5.2.4. The tr/// Operator (Transliteration)
5.3.1. Metasymbol Tables5.3.2. Specific Characters5.3.3. Wildcard Metasymbols
5.4.1. Custom Character Classes5.4.2. Classic Perl Character Class Shortcuts5.4.3. Unicode Properties5.4.3.1. Perl's Unicode properties5.4.3.2. Standard Unicode properties5.4.3.3. Unicode block properties5.4.3.4. Defining your own character properties5.4.4. POSIX-Style Character Classes
5.6.1. Beginnings: The \A and ^ Assertions5.6.2. Endings: The \z, \Z, and $ Assertions5.6.3. Boundaries: The \b and \B Assertions5.6.4. Progressive Matching5.6.5. Where You Left Off: The \G Assertion
5.7.1. Capturing5.7.2. Clustering5.7.3. Cloistered Pattern Modifiers
5.9.1. Letting Perl Do the Work5.9.2. Variable Interpolation5.9.2.1. When backslashes happen5.9.2.2. The qr// quote regex operator5.9.3. The Regex Compiler5.9.4. The Little Engine That /Could(n't)?/
5.10.1. Lookaround Assertions5.10.2. Nonbacktracking Subpatterns5.10.3. Programmatic Patterns5.10.3.1. Generated patterns5.10.3.2. Substitution evaluations5.10.3.3. Match-time code evaluation5.10.3.4. Match-time pattern interpolation5.10.3.5. Conditional interpolation5.10.4. Defining Your Own Assertions
6.1. Syntax
6.2.1. Tricks with Parameter Lists6.2.2. Error Indications6.2.3. Scoping Issues
6.4.1. Inlining Constant Functions6.4.2. Care with Prototypes
6.5.1. The locked and method Attributes6.5.2. The lvalue Attribute
7.1. Format Variables
7.2.1. Accessing Formatting Internals
8.1. What Is a Reference?
8.2.1. The Backslash Operator8.2.2. Anonymous Data8.2.2.1. The anonymous array composer8.2.2.2. The anonymous hash composer8.2.2.3. The anonymous subroutine composer8.2.3. Object Constructors8.2.4. Handle References8.2.5. Symbol Table References8.2.6. Implicit Creation of References
8.3.1. Using a Variable as a Variable Name8.3.2. Using a BLOCK as a Variable Name8.3.3. Using the Arrow Operator8.3.4. Using Object Methods8.3.5. Pseudohashes8.3.6. Other Tricks You Can Do with Hard References8.3.7. Closures8.3.7.1. Closures as function templates8.3.7.2. Nested subroutines
8.5.1. References Don't Work as Hash Keys8.5.2. Garbage Collection, Circular References, and Weak References
9.1. Arrays of Arrays9.1.1. Creating and Accessing a Two-Dimensional Array9.1.2. Growing Your Own9.1.3. Access and Printing9.1.4. Slices9.1.5. Common Mistakes
9.2.1. Composition of a Hash of Arrays9.2.2. Generation of a Hash of Arrays9.2.3. Access and Printing of a Hash of Arrays
9.3.1. Composition of an Array of Hashes9.3.2. Generation of an Array of Hashes9.3.3. Access and Printing of an Array of Hashes
9.4.1. Composition of a Hash of Hashes9.4.2. Generation of a Hash of Hashes9.4.3. Access and Printing of a Hash of Hashes
9.6.1. Composition, Access, and Printing of More Elaborate Records9.6.2. Composition, Access, and Printing of Even More Elaborate Records9.6.3. Generation of a Hash of Complex Records
10.1. Symbol Tables
11.1. Using Modules
11.2.1. Module Privacy and the Exporter11.2.1.1. Exporting without using Exporter's import method11.2.1.2. Version checking11.2.1.3. Managing unknown symbols11.2.1.4. Tag-handling utility functions
12.1. Brief Refresher on Object-Oriented Lingo
12.3.1. Method Invocation Using the Arrow Operator12.3.2. Method Invocation Using Indirect Objects12.3.3. Syntactic Snafus with Indirect Objects12.3.4. Package-Quoted Classes
12.4.1. Inheritable Constructors12.4.2. Initializers
12.5.1. Inheritance Through @ISA12.5.2. Accessing Overridden Methods12.5.3. UNIVERSAL: The Ultimate Ancestor Class12.5.4. Method Autoloading12.5.5. Private Methods
12.6.1. Garbage Collection with DESTROY Methods
12.7.1. Field Declarations with use fields12.7.2. Generating Classes with Class::Struct12.7.3. Generating Accessors with Autoloading12.7.4. Generating Accessors with Closures12.7.5. Using Closures for Private Objects12.7.6. New Tricks
13.1. The overload Pragma
14.1. Tying Scalars14.1.1. Scalar-Tying Methods14.1.2. Magical Counter Variables14.1.3. Magically Banishing $_
14.2.1. Array-Tying Methods14.2.2. Notational Convenience
14.3.1. Hash-Tying Methods
14.4.1. Filehandle-Tying Methods14.4.2. Creative Filehandles
15.1. Building Character
16.1. Signals16.1.1. Signaling Process Groups16.1.2. Reaping Zombies16.1.3. Timing Out Slow Operations16.1.4. Blocking Signals
16.2.1. File Locking16.2.2. Passing Filehandles
16.3.1. Anonymous Pipes16.3.2. Talking to Yourself16.3.3. Bidirectional Communication16.3.4. Named Pipes
16.5.1. Networking Clients16.5.2. Networking Servers16.5.3. Message Passing
17.1. The Process Model
17.2.1. The Thread Module17.2.1.1. Thread creation17.2.1.2. Thread destruction17.2.1.3. Catching exceptions from join17.2.1.4. The detach method17.2.1.5. Identifying threads17.2.1.6. Listing current threads17.2.1.7. Yielding the processor17.2.2. Data Access17.2.2.1. Synchronizing access with lock17.2.2.2. Deadlock17.2.2.3. Locking subroutines17.2.2.4. The locked attribute17.2.2.5. Locking methods17.2.2.6. Condition variables17.2.3. Other Thread Modules17.2.3.1. Queues17.2.3.2. Semaphores17.2.3.3. Other standard threading modules
18.1. The Life Cycle of a Perl Program
18.5.1. The Bytecode Generator18.5.2. The C Code Generators
19.1. Command Processing19.1.1. #! and Quoting on Non-Unix Systems19.1.2. Location of Perl19.1.3. Switches
20.1. Using the Debugger
20.2.1. Stepping and Running20.2.2. Breakpoints20.2.3. Tracing20.2.4. Display20.2.5. Locating Code20.2.6. Actions and Command Execution20.2.7. Miscellaneous Commands
20.3.1. Editor Support for Debugging20.3.2. Customizing with Init Files20.3.3. Debugger Options
20.5.1. Writing Your Own Debugger
21.1. How Perl Works
21.3.1. XS and XSUBs21.3.2. Creating Extensions21.3.3. XSUB Input and Output21.3.4. Using Functions from an External C Library
21.4.1. Compiling Embedded Programs21.4.2. Adding a Perl Interpreter to Your C Program21.4.3. Calling a Perl Subroutine from C21.4.4. Evaluating a Perl Statement from C21.4.5. Fiddling with the Perl Stack from C
22.1. The CPAN modules Directory
22.2.1. Decompressing and Unpacking CPAN Modules22.2.2. Building CPAN Modules22.2.3. Installing CPAN Modules into the Perl Library
22.3.1. Internal Testing22.3.2. External Testing
23.1. Handling Insecure Data23.1.1. Detecting and Laundering Tainted Data23.1.2. Cleaning Up Your Environment23.1.3. Accessing Commands and Files Under Reduced Privileges
23.2.1. Unix Kernel Security Bugs23.2.2. Handling Race Conditions23.2.3. Temporary Files
23.3.1. Safe Compartments23.3.1.1. Restricting namespace access23.3.1.2. Restricting operator access23.3.1.3. Safe examples23.3.2. Code Masquerading as Data
24.1. Common Goofs for Novices24.1.1. Universal Blunders24.1.2. Frequently Ignored Advice24.1.3. C Traps24.1.4. Shell Traps24.1.5. Previous Perl Traps
24.2.1. Time Efficiency24.2.2. Space Efficiency24.2.3. Programmer Efficiency24.2.4. Maintainer Efficiency24.2.5. Porter Efficiency24.2.6. User Efficiency
24.5.1. Generating Other Languages in Perl24.5.2. Generating Perl in Other Languages24.5.3. Source Filters
25.1. Newlines
26.1. Pod in a Nutshell26.1.1. Verbatim Paragraphs26.1.2. Pod Directives26.1.3. Pod Sequences
27.1. History Made Practical
28.1. Special Names Grouped by Type28.1.1. Regular Expression Special Variables28.1.2. Per-Filehandle Variables28.1.3. Per-Package Special Variables28.1.4. Program-wide Special Variables28.1.5. Per-Package Special Filehandles28.1.6. Per-Package Special Functions
29.1. Perl Functions by Category
29.2.1. abs29.2.2. accept29.2.3. alarm29.2.4. atan229.2.5. bind29.2.6. binmode29.2.7. bless29.2.8. caller29.2.9. chdir29.2.10. chmod29.2.11. chomp29.2.12. chop29.2.13. chown29.2.14. chr29.2.15. chroot29.2.16. close29.2.17. closedir29.2.18. connect29.2.19. cos29.2.20. crypt29.2.21. dbmclose29.2.22. dbmopen29.2.23. defined29.2.24. delete29.2.25. die29.2.26. do (block)29.2.27. do (file)29.2.28. do (subroutine)29.2.29. dump29.2.30. each29.2.31. eof29.2.32. eval29.2.33. exec29.2.34. exists29.2.35. exit29.2.36. exp29.2.37. fcntl29.2.38. fileno29.2.39. flock29.2.40. fork29.2.41. format29.2.42. formline29.2.43. getc29.2.44. getgrent29.2.45. getgrgid29.2.46. getgrnam29.2.47. gethostbyaddr29.2.48. gethostbyname29.2.49. gethostent29.2.50. getlogin29.2.51. getnetbyaddr29.2.52. getnetbyname29.2.53. getnetent29.2.54. getpeername29.2.55. getpgrp29.2.56. getppid29.2.57. getpriority29.2.58. getprotobyname29.2.59. getprotobynumber29.2.60. getprotoent29.2.61. getpwent29.2.62. getpwnam29.2.63. getpwuid29.2.64. getservbyname29.2.65. getservbyport29.2.66. getservent29.2.67. getsockname29.2.68. getsockopt29.2.69. glob29.2.70. gmtime29.2.71. goto29.2.72. grep29.2.73. hex29.2.74. import29.2.75. index29.2.76. int29.2.77. ioctl29.2.78. join29.2.79. keys29.2.80. kill29.2.81. last29.2.82. lc29.2.83. lcfirst29.2.84. length29.2.85. link29.2.86. listen29.2.87. local29.2.88. localtime29.2.89. lock29.2.90. log29.2.91. lstat29.2.92. m//29.2.93. map29.2.94. mkdir29.2.95. msgctl29.2.96. msgget29.2.97. msgrcv29.2.98. msgsnd29.2.99. my29.2.100. new29.2.101. next29.2.102. no29.2.103. oct29.2.104. open29.2.105. opendir29.2.106. ord29.2.107. our29.2.108. pack29.2.109. package29.2.110. pipe29.2.111. pop29.2.112. pos29.2.113. print29.2.114. printf29.2.115. prototype29.2.116. push29.2.117. q/STRING/29.2.118. quotemeta29.2.119. rand29.2.120. read29.2.121. readdir29.2.122. readline29.2.123. readlink29.2.124. readpipe29.2.125. recv29.2.126. redo29.2.127. ref29.2.128. rename29.2.129. require29.2.130. reset29.2.131. return29.2.132. reverse29.2.133. rewinddir29.2.134. rindex29.2.135. rmdir29.2.136. s///29.2.137. scalar29.2.138. seek29.2.139. seekdir29.2.140. select (output filehandle)29.2.141. select (ready file descriptors)29.2.142. semctl29.2.143. semget29.2.144. semop29.2.145. send29.2.146. setpgrp29.2.147. setpriority29.2.148. setsockopt29.2.149. shift29.2.150. shmctl29.2.151. shmget29.2.152. shmread29.2.153. shmwrite29.2.154. shutdown29.2.155. sin29.2.156. sleep29.2.157. socket29.2.158. socketpair29.2.159. sort29.2.160. splice29.2.161. split29.2.162. sprintf29.2.163. sqrt29.2.164. srand29.2.165. stat29.2.166. study29.2.167. sub29.2.168. substr29.2.169. symlink29.2.170. syscall29.2.171. sysopen29.2.172. sysread29.2.173. sysseek29.2.174. system29.2.175. syswrite29.2.176. tell29.2.177. telldir29.2.178. tie29.2.179. tied29.2.180. time29.2.181. times29.2.182. tr///29.2.183. truncate29.2.184. uc29.2.185. ucfirst29.2.186. umask29.2.187. undef29.2.188. unlink29.2.189. unpack29.2.190. unshift29.2.191. untie29.2.192. use29.2.193. utime29.2.194. values29.2.195. vec29.2.196. wait29.2.197. waitpid29.2.198. wantarray29.2.199. warn29.2.200. write29.2.201. //
30.1. Library Science
31.1. use attributes
31.7.1. Restrictions on use constant
31.10.1. use filetest 'access'
31.18.1. Signal Handlers31.18.2. Predefined Signal Lists31.18.3. Other Arguments to sigtrap31.18.4. Examples of sigtrap
31.19.1. strict 'refs'31.19.2. strict 'vars'31.19.3. strict 'subs'
32.1. Listings by Type32.1.1. Data Types32.1.2. String Processing, Language Text Processing, Parsing, and Searching32.1.3. Option, Argument, Parameter, and Configuration File Processing32.1.4. Filenames, Filesystems, and File Locking32.1.5. Filehandle, Directory Handle, and Stream I/O Utilities32.1.6. Internationalization and Locale32.1.7. Operating System Interfaces32.1.8. Networking and Interprocess Communication32.1.9. World Wide Web32.1.10. DBM Interfaces32.1.11. User Interfaces32.1.12. Authentication, Security, and Encryption32.1.13. Perl Language Extensions and Internals32.1.14. Convenient Classes32.1.15. Warnings and Exceptions32.1.16. Documentation Support32.1.17. Module Installation Support32.1.18. Development Support32.1.19. Perl Compiler and Code Generator32.1.20. Microsoft-Related Modules

Content preview from Programming Perl, 3rd Edition

Relational Operators

Perl has two classes of relational operators. One class operates on numeric values, the other on string values, as shown in Table 3.5.

Table 3-5. Relational Operators

Numeric	String	Meaning
`>`	`gt`	Greater than
`>=`	`ge`	Greater than or equal to
`<`	`lt`	Less than
`<=`	`le`	Less than or equal to

These operators return 1 for true and "" for false. Note that relational operators are nonassociating, which means that $a < $b < $c is a syntax error.

In the absence of locale declarations, string comparisons are based on the ASCII/Unicode collating sequences, and, unlike in some computer languages, trailing spaces count in the comparison. With a locale declaration, the collation order specified by the locale is used. (Locale-based collation mechanisms may or may not interact well with the Unicode collation mechanisms currently in development.)

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ISBN: 0596000278Supplemental Content Errata

Programming Perl, 3rd Edition

by Larry Wall, Tom Christiansen, Jon Orwant

Relational Operators

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.

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