Linux Blog

PERLMODLIB

Section: Perl Programmers Reference Guide (1)
Updated: 2006-01-07
Index Return to Main Contents
 

NAME

perlmodlib - constructing new Perl modules and finding existing ones  

THE PERL MODULE LIBRARY

Many modules are included in the Perl distribution. These are described below, and all end in .pm. You may discover compiled library files (usually ending in .so) or small pieces of modules to be autoloaded (ending in .al); these were automatically generated by the installation process. You may also discover files in the library directory that end in either .pl or .ph. These are old libraries supplied so that old programs that use them still run. The .pl files will all eventually be converted into standard modules, and the .ph files made by h2ph will probably end up as extension modules made by h2xs. (Some .ph values may already be available through the POSIX, Errno, or Fcntl modules.) The pl2pm file in the distribution may help in your conversion, but it's just a mechanical process and therefore far from bulletproof.  

Pragmatic Modules

They work somewhat like compiler directives (pragmata) in that they tend to affect the compilation of your program, and thus will usually work well only when used within a "use", or "no". Most of these are lexically scoped, so an inner BLOCK may countermand them by saying:

    no integer;
    no strict 'refs';
    no warnings;

which lasts until the end of that BLOCK.

Some pragmas are lexically scoped---typically those that affect the $^H hints variable. Others affect the current package instead, like "use vars" and "use subs", which allow you to predeclare a variables or subroutines within a particular file rather than just a block. Such declarations are effective for the entire file for which they were declared. You cannot rescind them with "no vars" or "no subs".

The following pragmas are defined (and have their own documentation).

attributes
Get/set subroutine or variable attributes
attrs
Set/get attributes of a subroutine (deprecated)
autouse
Postpone load of modules until a function is used
base
Establish IS-A relationship with base classes at compile time
bigint
Transparent BigInteger support for Perl
bignum
Transparent BigNumber support for Perl
bigrat
Transparent BigNumber/BigRational support for Perl
blib
Use MakeMaker's uninstalled version of a package
bytes
Force byte semantics rather than character semantics
charnames
Define character names for "\N{named}" string literal escapes
constant
Declare constants
diagnostics
Produce verbose warning diagnostics
encoding
Allows you to write your script in non-ascii or non-utf8
fields
Compile-time class fields
filetest
Control the filetest permission operators
if
"use" a Perl module if a condition holds
integer
Use integer arithmetic instead of floating point
less
Request less of something from the compiler
lib
Manipulate @INC at compile time
locale
Use and avoid POSIX locales for built-in operations
open
Set default PerlIO layers for input and output
ops
Restrict unsafe operations when compiling
overload
Package for overloading Perl operations
re
Alter regular expression behaviour
sigtrap
Enable simple signal handling
sort
Control sort() behaviour
strict
Restrict unsafe constructs
subs
Predeclare sub names
threads
Perl extension allowing use of interpreter based threads from perl
threads::shared
Perl extension for sharing data structures between threads
utf8
Enable/disable UTF-8 (or UTF-EBCDIC) in source code
vars
Predeclare global variable names (obsolete)
vmsish
Control VMS-specific language features
warnings
Control optional warnings
warnings::register
Warnings import function
 

Standard Modules

Standard, bundled modules are all expected to behave in a well-defined manner with respect to namespace pollution because they use the Exporter module. See their own documentation for details.

It's possible that not all modules listed below are installed on your system. For example, the GDBM_File module will not be installed if you don't have the gdbm library.

AnyDBM_File
Provide framework for multiple DBMs
Attribute::Handlers
Simpler definition of attribute handlers
AutoLoader
Load subroutines only on demand
AutoSplit
Split a package for autoloading
B
The Perl Compiler
B::Asmdata
Autogenerated data about Perl ops, used to generate bytecode
B::Assembler
Assemble Perl bytecode
B::Bblock
Walk basic blocks
B::Bytecode
Perl compiler's bytecode backend
B::C
Perl compiler's C backend
B::CC
Perl compiler's optimized C translation backend
B::Concise
Walk Perl syntax tree, printing concise info about ops
B::Debug
Walk Perl syntax tree, printing debug info about ops
B::Deparse
Perl compiler backend to produce perl code
B::Disassembler
Disassemble Perl bytecode
B::Lint
Perl lint
B::Showlex
Show lexical variables used in functions or files
B::Stackobj
Helper module for CC backend
B::Stash
Show what stashes are loaded
B::Terse
Walk Perl syntax tree, printing terse info about ops
B::Xref
Generates cross reference reports for Perl programs
Benchmark
Benchmark running times of Perl code
ByteLoader
Load byte compiled perl code
CGI
Simple Common Gateway Interface Class
CGI::Apache
Backward compatibility module for CGI.pm
CGI::Carp
CGI routines for writing to the HTTPD (or other) error log
CGI::Cookie
Interface to Netscape Cookies
CGI::Fast
CGI Interface for Fast CGI
CGI::Pretty
Module to produce nicely formatted HTML code
CGI::Push
Simple Interface to Server Push
CGI::Switch
Backward compatibility module for defunct CGI::Switch
CGI::Util
Internal utilities used by CGI module
CPAN
Query, download and build perl modules from CPAN sites
CPAN::FirstTime
Utility for CPAN::Config file Initialization
CPAN::Nox
Wrapper around CPAN.pm without using any XS module
CPAN::Version
Utility functions to compare CPAN versions
Carp
Warn of errors (from perspective of caller)
Carp::Heavy
Heavy machinery, no user serviceable parts inside
Class::ISA
Report the search path for a class's ISA tree
Class::Struct
Declare struct-like datatypes as Perl classes
Config
Access Perl configuration information
Cwd
Get pathname of current working directory
DB
Programmatic interface to the Perl debugging API (draft, subject to
DBM_Filter
Filter DBM keys/values
DB_File
Perl5 access to Berkeley DB version 1.x
Data::Dumper
Stringified perl data structures, suitable for both printing and "eval"
Devel::DProf
A Perl code profiler
Devel::PPPort
Perl/Pollution/Portability
Devel::Peek
A data debugging tool for the XS programmer
Devel::SelfStubber
Generate stubs for a SelfLoading module
Digest
Modules that calculate message digests
Digest::MD5
Perl interface to the MD5 Algorithm
Digest::base
Digest base class
Digest::file
Calculate digests of files
DirHandle
Supply object methods for directory handles
Dumpvalue
Provides screen dump of Perl data.
DynaLoader
Dynamically load C libraries into Perl code
Encode
Character encodings
Encode::Alias
Alias definitions to encodings
Encode::Byte
Single Byte Encodings
Encode::CJKConstants
Internally used by Encode::??::ISO_2022_*
Encode::CN
China-based Chinese Encodings
Encode::CN::HZ
Internally used by Encode::CN
Encode::Config
Internally used by Encode
Encode::EBCDIC
EBCDIC Encodings
Encode::Encoder
Object Oriented Encoder
Encode::Encoding
Encode Implementation Base Class
Encode::Guess
Guesses encoding from data
Encode::JP
Japanese Encodings
Encode::JP::H2Z
Internally used by Encode::JP::2022_JP*
Encode::JP::JIS7
Internally used by Encode::JP
Encode::KR
Korean Encodings
Encode::KR::2022_KR
Internally used by Encode::KR
Encode::MIME::Header
MIME 'B' and 'Q' header encoding
Encode::PerlIO
A detailed document on Encode and PerlIO
Encode::Supported
Encodings supported by Encode
Encode::Symbol
Symbol Encodings
Encode::TW
Taiwan-based Chinese Encodings
Encode::Unicode
Various Unicode Transformation Formats
Encode::Unicode::UTF7
UTF-7 encoding
English
Use nice English (or awk) names for ugly punctuation variables
Env
Perl module that imports environment variables as scalars or arrays
Errno
System errno constants
Exporter
Implements default import method for modules
Exporter::Heavy
Exporter guts
ExtUtils::Command
Utilities to replace common UNIX commands in Makefiles etc.
ExtUtils::Command::MM
Commands for the MM's to use in Makefiles
ExtUtils::Constant
Generate XS code to import C header constants
ExtUtils::Constant::Base
Base class for ExtUtils::Constant objects
ExtUtils::Constant::Utils
Helper functions for ExtUtils::Constant
ExtUtils::Constant::XS
Base class for ExtUtils::Constant objects
ExtUtils::Embed
Utilities for embedding Perl in C/C++ applications
ExtUtils::Install
Install files from here to there
ExtUtils::Installed
Inventory management of installed modules
ExtUtils::Liblist
Determine libraries to use and how to use them
ExtUtils::MM
OS adjusted ExtUtils::MakeMaker subclass
ExtUtils::MM_AIX
AIX specific subclass of ExtUtils::MM_Unix
ExtUtils::MM_Any
Platform-agnostic MM methods
ExtUtils::MM_BeOS
Methods to override UN*X behaviour in ExtUtils::MakeMaker
ExtUtils::MM_Cygwin
Methods to override UN*X behaviour in ExtUtils::MakeMaker
ExtUtils::MM_DOS
DOS specific subclass of ExtUtils::MM_Unix
ExtUtils::MM_MacOS
Once produced Makefiles for MacOS Classic
ExtUtils::MM_NW5
Methods to override UN*X behaviour in ExtUtils::MakeMaker
ExtUtils::MM_OS2
Methods to override UN*X behaviour in ExtUtils::MakeMaker
ExtUtils::MM_QNX
QNX specific subclass of ExtUtils::MM_Unix
ExtUtils::MM_UWIN
U/WIN specific subclass of ExtUtils::MM_Unix
ExtUtils::MM_Unix
Methods used by ExtUtils::MakeMaker
ExtUtils::MM_VMS
Methods to override UN*X behaviour in ExtUtils::MakeMaker
ExtUtils::MM_VOS
VOS specific subclass of ExtUtils::MM_Unix
ExtUtils::MM_Win32
Methods to override UN*X behaviour in ExtUtils::MakeMaker
ExtUtils::MM_Win95
Method to customize MakeMaker for Win9X
ExtUtils::MY
ExtUtils::MakeMaker subclass for customization
ExtUtils::MakeMaker
Create a module Makefile
ExtUtils::MakeMaker::Config
Wrapper around Config.pm
ExtUtils::MakeMaker::FAQ
Frequently Asked Questions About MakeMaker
ExtUtils::MakeMaker::Tutorial
Writing a module with MakeMaker
ExtUtils::MakeMaker::bytes
Version-agnostic bytes.pm
ExtUtils::MakeMaker::vmsish
Platform-agnostic vmsish.pm
ExtUtils::Manifest
Utilities to write and check a MANIFEST file
ExtUtils::Mkbootstrap
Make a bootstrap file for use by DynaLoader
ExtUtils::Mksymlists
Write linker options files for dynamic extension
ExtUtils::Packlist
Manage .packlist files
ExtUtils::testlib
Add blib/* directories to @INC
Fatal
Replace functions with equivalents which succeed or die
Fcntl
Load the C Fcntl.h defines
File::Basename
Parse file paths into directory, filename and suffix.
File::CheckTree
Run many filetest checks on a tree
File::Compare
Compare files or filehandles
File::Copy
Copy files or filehandles
File::DosGlob
DOS like globbing and then some
File::Find
Traverse a directory tree.
File::Glob
Perl extension for BSD glob routine
File::Path
Create or remove directory trees
File::Spec
Portably perform operations on file names
File::Spec::Cygwin
Methods for Cygwin file specs
File::Spec::Epoc
Methods for Epoc file specs
File::Spec::Functions
Portably perform operations on file names
File::Spec::Mac
File::Spec for Mac OS (Classic)
File::Spec::OS2
Methods for OS/2 file specs
File::Spec::Unix
File::Spec for Unix, base for other File::Spec modules
File::Spec::VMS
Methods for VMS file specs
File::Spec::Win32
Methods for Win32 file specs
File::Temp
Return name and handle of a temporary file safely
File::stat
By-name interface to Perl's built-in stat() functions
FileCache
Keep more files open than the system permits
FileHandle
Supply object methods for filehandles
Filter::Simple
Simplified source filtering
Filter::Util::Call
Perl Source Filter Utility Module
FindBin
Locate directory of original perl script
GDBM_File
Perl5 access to the gdbm library.
Getopt::Long
Extended processing of command line options
Getopt::Std
Process single-character switches with switch clustering
Hash::Util
A selection of general-utility hash subroutines
I18N::Collate
Compare 8-bit scalar data according to the current locale
I18N::LangTags
Functions for dealing with RFC3066-style language tags
I18N::LangTags::Detect
Detect the user's language preferences
I18N::LangTags::List
Tags and names for human languages
I18N::Langinfo
Query locale information
IO
Load various IO modules
IO::Dir
Supply object methods for directory handles
IO::File
Supply object methods for filehandles
IO::Handle
Supply object methods for I/O handles
IO::Pipe
Supply object methods for pipes
IO::Poll
Object interface to system poll call
IO::Seekable
Supply seek based methods for I/O objects
IO::Select
OO interface to the select system call
IO::Socket
Object interface to socket communications
IO::Socket::INET
Object interface for AF_INET domain sockets
IO::Socket::UNIX
Object interface for AF_UNIX domain sockets
IPC::Open2
Open a process for both reading and writing
IPC::Open3
Open a process for reading, writing, and error handling
IPC::SysV
SysV IPC constants
IPC::SysV::Msg
SysV Msg IPC object class
IPC::SysV::Semaphore
SysV Semaphore IPC object class
List::Util
A selection of general-utility list subroutines
Locale::Constants
Constants for Locale codes
Locale::Country
ISO codes for country identification (ISO 3166)
Locale::Currency
ISO three letter codes for currency identification (ISO 4217)
Locale::Language
ISO two letter codes for language identification (ISO 639)
Locale::Maketext
Framework for localization
Locale::Maketext::TPJ13
Article about software localization
Locale::Script
ISO codes for script identification (ISO 15924)
MIME::Base64
Encoding and decoding of base64 strings
MIME::Base64::QuotedPrint
Encoding and decoding of quoted-printable strings
Math::BigFloat
Arbitrary size floating point math package
Math::BigInt
Arbitrary size integer/float math package
Math::BigInt::Calc
Pure Perl module to support Math::BigInt
Math::BigInt::CalcEmu
Emulate low-level math with BigInt code
Math::BigRat
Arbitrary big rational numbers
Math::Complex
Complex numbers and associated mathematical functions
Math::Trig
Trigonometric functions
Memoize
Make functions faster by trading space for time
Memoize::AnyDBM_File
Glue to provide EXISTS for AnyDBM_File for Storable use
Memoize::Expire
Plug-in module for automatic expiration of memoized values
Memoize::ExpireFile
Test for Memoize expiration semantics
Memoize::ExpireTest
Test for Memoize expiration semantics
Memoize::NDBM_File
Glue to provide EXISTS for NDBM_File for Storable use
Memoize::SDBM_File
Glue to provide EXISTS for SDBM_File for Storable use
Memoize::Storable
Store Memoized data in Storable database
NDBM_File
Tied access to ndbm files
NEXT
Provide a pseudo-class NEXT (et al) that allows method redispatch
Net::Cmd
Network Command class (as used by FTP, SMTP etc)
Net::Config
Local configuration data for libnet
Net::Domain
Attempt to evaluate the current host's internet name and domain
Net::FTP
FTP Client class
Net::NNTP
NNTP Client class
Net::Netrc
OO interface to users netrc file
Net::POP3
Post Office Protocol 3 Client class (RFC1939)
Net::Ping
Check a remote host for reachability
Net::SMTP
Simple Mail Transfer Protocol Client
Net::Time
Time and daytime network client interface
Net::hostent
By-name interface to Perl's built-in gethost*() functions
Net::libnetFAQ
Libnet Frequently Asked Questions
Net::netent
By-name interface to Perl's built-in getnet*() functions
Net::protoent
By-name interface to Perl's built-in getproto*() functions
Net::servent
By-name interface to Perl's built-in getserv*() functions
O
Generic interface to Perl Compiler backends
ODBM_File
Tied access to odbm files
Opcode
Disable named opcodes when compiling perl code
POSIX
Perl interface to IEEE Std 1003.1
PerlIO
On demand loader for PerlIO layers and root of PerlIO::* name space
PerlIO::encoding
Encoding layer
PerlIO::scalar
In-memory IO, scalar IO
PerlIO::via
Helper class for PerlIO layers implemented in perl
PerlIO::via::QuotedPrint
PerlIO layer for quoted-printable strings
Pod::Checker
Check pod documents for syntax errors
Pod::Find
Find POD documents in directory trees
Pod::Functions
Group Perl's functions a la perlfunc.pod
Pod::Html
Module to convert pod files to HTML
Pod::InputObjects
Objects representing POD input paragraphs, commands, etc.
Pod::LaTeX
Convert Pod data to formatted Latex
Pod::Man
Convert POD data to formatted *roff input
Pod::ParseLink
Parse an L<> formatting code in POD text
Pod::ParseUtils
Helpers for POD parsing and conversion
Pod::Parser
Base class for creating POD filters and translators
Pod::Perldoc::ToChecker
Let Perldoc check Pod for errors
Pod::Perldoc::ToMan
Let Perldoc render Pod as man pages
Pod::Perldoc::ToNroff
Let Perldoc convert Pod to nroff
Pod::Perldoc::ToPod
Let Perldoc render Pod as ... Pod!
Pod::Perldoc::ToRtf
Let Perldoc render Pod as RTF
Pod::Perldoc::ToText
Let Perldoc render Pod as plaintext
Pod::Perldoc::ToTk
Let Perldoc use Tk::Pod to render Pod
Pod::Perldoc::ToXml
Let Perldoc render Pod as XML
Pod::PlainText
Convert POD data to formatted ASCII text
Pod::Plainer
Perl extension for converting Pod to old style Pod.
Pod::Select
Extract selected sections of POD from input
Pod::Text
Convert POD data to formatted ASCII text
Pod::Text::Color
Convert POD data to formatted color ASCII text
Pod::Text::Overstrike
Convert POD data to formatted overstrike text
Pod::Text::Termcap
Convert POD data to ASCII text with format escapes
Pod::Usage
Print a usage message from embedded pod documentation
SDBM_File
Tied access to sdbm files
Safe
Compile and execute code in restricted compartments
Scalar::Util
A selection of general-utility scalar subroutines
Search::Dict
Search for key in dictionary file
SelectSaver
Save and restore selected file handle
SelfLoader
Load functions only on demand
Shell
Run shell commands transparently within perl
Socket
Load the C socket.h defines and structure manipulators
Storable
Persistence for Perl data structures
Switch
A switch statement for Perl
Symbol
Manipulate Perl symbols and their names
Sys::Hostname
Try every conceivable way to get hostname
Sys::Syslog
Perl interface to the UNIX syslog(3) calls
Term::ANSIColor
Color screen output using ANSI escape sequences
Term::Cap
Perl termcap interface
Term::Complete
Perl word completion module
Term::ReadLine
Perl interface to various "readline" packages.
Test
Provides a simple framework for writing test scripts
Test::Builder
Backend for building test libraries
Test::Builder::Module
Base class for test modules
Test::Builder::Tester
Test testsuites that have been built with
Test::Builder::Tester::Color
Turn on colour in Test::Builder::Tester
Test::Harness
Run Perl standard test scripts with statistics
Test::Harness::Assert
Simple assert
Test::Harness::Iterator
Internal Test::Harness Iterator
Test::Harness::Point
Object for tracking a single test point
Test::Harness::Straps
Detailed analysis of test results
Test::Harness::TAP
Documentation for the TAP format
Test::More
Yet another framework for writing test scripts
Test::Simple
Basic utilities for writing tests.
Test::Tutorial
A tutorial about writing really basic tests
Text::Abbrev
Create an abbreviation table from a list
Text::Balanced
Extract delimited text sequences from strings.
Text::ParseWords
Parse text into an array of tokens or array of arrays
Text::Soundex
Implementation of the Soundex Algorithm as Described by Knuth
Text::Tabs
Expand and unexpand tabs per the unix expand(1) and unexpand(1)
Text::Wrap
Line wrapping to form simple paragraphs
Thread
Manipulate threads in Perl (for old code only)
Thread::Queue
Thread-safe queues
Thread::Semaphore
Thread-safe semaphores
Thread::Signal
Start a thread which runs signal handlers reliably (for old code)
Thread::Specific
Thread-specific keys
Tie::Array
Base class for tied arrays
Tie::File
Access the lines of a disk file via a Perl array
Tie::Handle
Base class definitions for tied handles
Tie::Hash
Base class definitions for tied hashes
Tie::Memoize
Add data to hash when needed
Tie::RefHash
Use references as hash keys
Tie::Scalar
Base class definitions for tied scalars
Tie::SubstrHash
Fixed-table-size, fixed-key-length hashing
Time::HiRes
High resolution alarm, sleep, gettimeofday, interval timers
Time::Local
Efficiently compute time from local and GMT time
Time::gmtime
By-name interface to Perl's built-in gmtime() function
Time::localtime
By-name interface to Perl's built-in localtime() function
Time::tm
Internal object used by Time::gmtime and Time::localtime
UNIVERSAL
Base class for ALL classes (blessed references)
Unicode::Collate
Unicode Collation Algorithm
Unicode::Normalize
Unicode Normalization Forms
Unicode::UCD
Unicode character database
User::grent
By-name interface to Perl's built-in getgr*() functions
User::pwent
By-name interface to Perl's built-in getpw*() functions
XS::APItest
Test the perl C API
XS::Typemap
Module to test the XS typemaps distributed with perl
XSLoader
Dynamically load C libraries into Perl code

To find out all modules installed on your system, including those without documentation or outside the standard release, just use the following command (under the default win32 shell, double quotes should be used instead of single quotes).

    % perl -MFile::Find=find -MFile::Spec::Functions -Tlwe \
      'find { wanted => sub { print canonpath $_ if /\.pm\z/ },
      no_chdir => 1 }, @INC'

(The -T is here to prevent '.' from being listed in @INC.) They should all have their own documentation installed and accessible via your system man(1) command. If you do not have a find program, you can use the Perl find2perl program instead, which generates Perl code as output you can run through perl. If you have a man program but it doesn't find your modules, you'll have to fix your manpath. See perl for details. If you have no system man command, you might try the perldoc program.

Note also that the command "perldoc perllocal" gives you a (possibly incomplete) list of the modules that have been further installed on your system. (The perllocal.pod file is updated by the standard MakeMaker install process.)  

Extension Modules

Extension modules are written in C (or a mix of Perl and C). They are usually dynamically loaded into Perl if and when you need them, but may also be linked in statically. Supported extension modules include Socket, Fcntl, and POSIX.

Many popular C extension modules do not come bundled (at least, not completely) due to their sizes, volatility, or simply lack of time for adequate testing and configuration across the multitude of platforms on which Perl was beta-tested. You are encouraged to look for them on CPAN (described below), or using web search engines like Alta Vista or Google.  

CPAN

CPAN stands for Comprehensive Perl Archive Network; it's a globally replicated trove of Perl materials, including documentation, style guides, tricks and traps, alternate ports to non-Unix systems and occasional binary distributions for these. Search engines for CPAN can be found at http://www.cpan.org/

Most importantly, CPAN includes around a thousand unbundled modules, some of which require a C compiler to build. Major categories of modules are:

*
Language Extensions and Documentation Tools
*
Development Support
*
Operating System Interfaces
*
Networking, Device Control (modems) and InterProcess Communication
*
Data Types and Data Type Utilities
*
Database Interfaces
*
User Interfaces
*
Interfaces to / Emulations of Other Programming Languages
*
File Names, File Systems and File Locking (see also File Handles)
*
String Processing, Language Text Processing, Parsing, and Searching
*
Option, Argument, Parameter, and Configuration File Processing
*
Internationalization and Locale
*
Authentication, Security, and Encryption
*
World Wide Web, HTML, HTTP, CGI, MIME
*
Server and Daemon Utilities
*
Archiving and Compression
*
Images, Pixmap and Bitmap Manipulation, Drawing, and Graphing
*
Mail and Usenet News
*
Control Flow Utilities (callbacks and exceptions etc)
*
File Handle and Input/Output Stream Utilities
*
Miscellaneous Modules

The list of the registered CPAN sites as of this writing follows. Please note that the sorting order is alphabetical on fields:

Continent
   |
   |-->Country
         |
         |-->[state/province]
                   |
                   |-->ftp
                   |
                   |-->[http]

and thus the North American servers happen to be listed between the European and the South American sites.

You should try to choose one close to you.  

Africa

South Africa
                      http://ftp.rucus.ru.ac.za/pub/perl/CPAN/
                      ftp://ftp.rucus.ru.ac.za/pub/perl/CPAN/
                      ftp://ftp.is.co.za/programming/perl/CPAN/
                      ftp://ftp.saix.net/pub/CPAN/
                      ftp://ftp.sun.ac.za/CPAN/CPAN/

 

Asia

China
                      http://cpan.linuxforum.net/
                      http://cpan.shellhung.org/
                      ftp://ftp.shellhung.org/pub/CPAN
                      ftp://mirrors.hknet.com/CPAN

Indonesia
                      http://mirrors.tf.itb.ac.id/cpan/
                      http://cpan.cbn.net.id/
                      ftp://ftp.cbn.net.id/mirror/CPAN

Israel
                      ftp://ftp.iglu.org.il/pub/CPAN/
                      http://cpan.lerner.co.il/
                      http://bioinfo.weizmann.ac.il/pub/software/perl/CPAN/
                      ftp://bioinfo.weizmann.ac.il/pub/software/perl/CPAN/

Japan
                      ftp://ftp.u-aizu.ac.jp/pub/CPAN
                      ftp://ftp.kddlabs.co.jp/CPAN/
                      ftp://ftp.ayamura.org/pub/CPAN/
                      ftp://ftp.jaist.ac.jp/pub/lang/perl/CPAN/
                      http://ftp.cpan.jp/
                      ftp://ftp.cpan.jp/CPAN/
                      ftp://ftp.dti.ad.jp/pub/lang/CPAN/
                      ftp://ftp.ring.gr.jp/pub/lang/perl/CPAN/

Malaysia
                      http://cpan.MyBSD.org.my
                      http://mirror.leafbug.org/pub/CPAN
                      http://ossig.mncc.com.my/mirror/pub/CPAN

Russian Federation
                      http://cpan.tomsk.ru
                      ftp://cpan.tomsk.ru/

Saudi Arabia
                      ftp://ftp.isu.net.sa/pub/CPAN/

Singapore
                      http://CPAN.en.com.sg/
                      ftp://cpan.en.com.sg/
                      http://mirror.averse.net/pub/CPAN
                      ftp://mirror.averse.net/pub/CPAN
                      http://cpan.oss.eznetsols.org
                      ftp://ftp.oss.eznetsols.org/cpan

South Korea
                      http://CPAN.bora.net/
                      ftp://ftp.bora.net/pub/CPAN/
                      http://mirror.kr.FreeBSD.org/CPAN
                      ftp://ftp.kr.FreeBSD.org/pub/CPAN

Taiwan
                      ftp://ftp.nctu.edu.tw/UNIX/perl/CPAN
                      http://cpan.cdpa.nsysu.edu.tw/
                      ftp://cpan.cdpa.nsysu.edu.tw/pub/CPAN
                      http://ftp.isu.edu.tw/pub/CPAN
                      ftp://ftp.isu.edu.tw/pub/CPAN
                      ftp://ftp1.sinica.edu.tw/pub1/perl/CPAN/
                      http://ftp.tku.edu.tw/pub/CPAN/
                      ftp://ftp.tku.edu.tw/pub/CPAN/

Thailand
                      ftp://ftp.loxinfo.co.th/pub/cpan/
                      ftp://ftp.cs.riubon.ac.th/pub/mirrors/CPAN/

 

Central America

Costa Rica
                      http://ftp.ucr.ac.cr/Unix/CPAN/
                      ftp://ftp.ucr.ac.cr/pub/Unix/CPAN/

 

Europe

Austria
                      http://cpan.inode.at/
                      ftp://cpan.inode.at
                      ftp://ftp.tuwien.ac.at/pub/CPAN/

Belgium
                      http://ftp.easynet.be/pub/CPAN/
                      ftp://ftp.easynet.be/pub/CPAN/
                      http://cpan.skynet.be
                      ftp://ftp.cpan.skynet.be/pub/CPAN
                      ftp://ftp.kulnet.kuleuven.ac.be/pub/mirror/CPAN/

Bosnia and Herzegovina
                      http://cpan.blic.net/

Bulgaria
                      http://cpan.online.bg
                      ftp://cpan.online.bg/cpan
                      http://cpan.zadnik.org
                      ftp://ftp.zadnik.org/mirrors/CPAN/
                      http://cpan.lirex.net/
                      ftp://ftp.lirex.net/pub/mirrors/CPAN

Croatia
                      http://ftp.linux.hr/pub/CPAN/
                      ftp://ftp.linux.hr/pub/CPAN/

Czech Republic
                      ftp://ftp.fi.muni.cz/pub/CPAN/
                      ftp://sunsite.mff.cuni.cz/MIRRORS/ftp.funet.fi/pub/languages/perl/CPAN/

Denmark
                      http://mirrors.sunsite.dk/cpan/
                      ftp://sunsite.dk/mirrors/cpan/
                      http://cpan.cybercity.dk
                      http://www.cpan.dk/CPAN/
                      ftp://www.cpan.dk/ftp.cpan.org/CPAN/

Estonia
                      ftp://ftp.ut.ee/pub/languages/perl/CPAN/

Finland
                      ftp://ftp.funet.fi/pub/languages/perl/CPAN/
                      http://mirror.eunet.fi/CPAN

France
                      http://www.enstimac.fr/Perl/CPAN
                      http://ftp.u-paris10.fr/perl/CPAN
                      ftp://ftp.u-paris10.fr/perl/CPAN
                      http://cpan.mirrors.easynet.fr/
                      ftp://cpan.mirrors.easynet.fr/pub/ftp.cpan.org/
                      ftp://ftp.club-internet.fr/pub/perl/CPAN/
                      http://fr.cpan.org/
                      ftp://ftp.lip6.fr/pub/perl/CPAN/
                      ftp://ftp.oleane.net/pub/mirrors/CPAN/
                      ftp://ftp.pasteur.fr/pub/computing/CPAN/
                      http://mir2.ovh.net/ftp.cpan.org
                      ftp://mir1.ovh.net/ftp.cpan.org
                      http://ftp.crihan.fr/mirrors/ftp.cpan.org/
                      ftp://ftp.crihan.fr/mirrors/ftp.cpan.org/
                      http://ftp.u-strasbg.fr/CPAN
                      ftp://ftp.u-strasbg.fr/CPAN
                      ftp://cpan.cict.fr/pub/CPAN/
                      ftp://ftp.uvsq.fr/pub/perl/CPAN/

Germany
                      ftp://ftp.rub.de/pub/CPAN/
                      ftp://ftp.freenet.de/pub/ftp.cpan.org/pub/CPAN/
                      ftp://ftp.uni-erlangen.de/pub/source/CPAN/
                      ftp://ftp-stud.fht-esslingen.de/pub/Mirrors/CPAN
                      http://pandemonium.tiscali.de/pub/CPAN/
                      ftp://pandemonium.tiscali.de/pub/CPAN/
                      http://ftp.gwdg.de/pub/languages/perl/CPAN/
                      ftp://ftp.gwdg.de/pub/languages/perl/CPAN/
                      ftp://ftp.uni-hamburg.de/pub/soft/lang/perl/CPAN/
                      ftp://ftp.leo.org/pub/CPAN/
                      http://cpan.noris.de/
                      ftp://cpan.noris.de/pub/CPAN/
                      ftp://ftp.mpi-sb.mpg.de/pub/perl/CPAN/
                      ftp://ftp.gmd.de/mirrors/CPAN/

Greece
                      ftp://ftp.acn.gr/pub/lang/perl
                      ftp://ftp.forthnet.gr/pub/languages/perl/CPAN
                      ftp://ftp.ntua.gr/pub/lang/perl/

Hungary
                      http://ftp.kfki.hu/packages/perl/CPAN/
                      ftp://ftp.kfki.hu/pub/packages/perl/CPAN/

Iceland
                      http://ftp.rhnet.is/pub/CPAN/
                      ftp://ftp.rhnet.is/pub/CPAN/

Ireland
                      http://cpan.indigo.ie/
                      ftp://cpan.indigo.ie/pub/CPAN/
                      http://ftp.heanet.ie/mirrors/ftp.perl.org/pub/CPAN
                      ftp://ftp.heanet.ie/mirrors/ftp.perl.org/pub/CPAN
                      http://sunsite.compapp.dcu.ie/pub/perl/
                      ftp://sunsite.compapp.dcu.ie/pub/perl/

Italy
                      http://cpan.nettuno.it/
                      http://gusp.dyndns.org/CPAN/
                      ftp://gusp.dyndns.org/pub/CPAN
                      http://softcity.iol.it/cpan
                      ftp://softcity.iol.it/pub/cpan
                      ftp://ftp.unina.it/pub/Other/CPAN/CPAN/
                      ftp://ftp.unipi.it/pub/mirror/perl/CPAN/
                      ftp://cis.uniRoma2.it/CPAN/
                      ftp://ftp.edisontel.it/pub/CPAN_Mirror/
                      http://cpan.flashnet.it/
                      ftp://ftp.flashnet.it/pub/CPAN/

Latvia
                      http://kvin.lv/pub/CPAN/

Lithuania
                      ftp://ftp.unix.lt/pub/CPAN/

Netherlands
                      ftp://download.xs4all.nl/pub/mirror/CPAN/
                      ftp://ftp.nl.uu.net/pub/CPAN/
                      ftp://ftp.nluug.nl/pub/languages/perl/CPAN/
                      http://cpan.cybercomm.nl/
                      ftp://mirror.cybercomm.nl/pub/CPAN
                      ftp://mirror.vuurwerk.nl/pub/CPAN/
                      ftp://ftp.cpan.nl/pub/CPAN/
                      http://ftp.easynet.nl/mirror/CPAN
                      ftp://ftp.easynet.nl/mirror/CPAN
                      http://archive.cs.uu.nl/mirror/CPAN/
                      ftp://ftp.cs.uu.nl/mirror/CPAN/

Norway
                      ftp://ftp.uninett.no/pub/languages/perl/CPAN
                      ftp://ftp.uit.no/pub/languages/perl/cpan/

Poland
                      ftp://ftp.mega.net.pl/CPAN
                      ftp://ftp.man.torun.pl/pub/doc/CPAN/
                      ftp://sunsite.icm.edu.pl/pub/CPAN/

Portugal
                      ftp://ftp.ua.pt/pub/CPAN/
                      ftp://perl.di.uminho.pt/pub/CPAN/
                      http://cpan.dei.uc.pt/
                      ftp://ftp.dei.uc.pt/pub/CPAN
                      ftp://ftp.nfsi.pt/pub/CPAN
                      http://ftp.linux.pt/pub/mirrors/CPAN
                      ftp://ftp.linux.pt/pub/mirrors/CPAN
                      http://cpan.ip.pt/
                      ftp://cpan.ip.pt/pub/cpan/
                      http://cpan.telepac.pt/
                      ftp://ftp.telepac.pt/pub/cpan/

Romania
                      ftp://ftp.bio-net.ro/pub/CPAN
                      ftp://ftp.kappa.ro/pub/mirrors/ftp.perl.org/pub/CPAN/
                      ftp://ftp.lug.ro/CPAN
                      ftp://ftp.roedu.net/pub/CPAN/
                      ftp://ftp.dntis.ro/pub/cpan/
                      ftp://ftp.iasi.roedu.net/pub/mirrors/ftp.cpan.org/
                      http://cpan.ambra.ro/
                      ftp://ftp.ambra.ro/pub/CPAN
                      ftp://ftp.dnttm.ro/pub/CPAN/
                      ftp://ftp.lasting.ro/pub/CPAN
                      ftp://ftp.timisoara.roedu.net/mirrors/CPAN/

Russia
                      ftp://ftp.chg.ru/pub/lang/perl/CPAN/
                      http://cpan.rinet.ru/
                      ftp://cpan.rinet.ru/pub/mirror/CPAN/
                      ftp://ftp.aha.ru/pub/CPAN/
                      ftp://ftp.corbina.ru/pub/CPAN/
                      http://cpan.sai.msu.ru/
                      ftp://ftp.sai.msu.su/pub/lang/perl/CPAN/

Slovakia
                      ftp://ftp.cvt.stuba.sk/pub/CPAN/

Slovenia
                      ftp://ftp.arnes.si/software/perl/CPAN/

Spain
                      http://cpan.imasd.elmundo.es/
                      ftp://ftp.rediris.es/mirror/CPAN/
                      ftp://ftp.ri.telefonica-data.net/CPAN
                      ftp://ftp.etse.urv.es/pub/perl/

Sweden
                      http://ftp.du.se/CPAN/
                      ftp://ftp.du.se/pub/CPAN/
                      http://mirror.dataphone.se/CPAN
                      ftp://mirror.dataphone.se/pub/CPAN
                      ftp://ftp.sunet.se/pub/lang/perl/CPAN/

Switzerland
                      http://cpan.mirror.solnet.ch/
                      ftp://ftp.solnet.ch/mirror/CPAN/
                      ftp://ftp.danyk.ch/CPAN/
                      ftp://sunsite.cnlab-switch.ch/mirror/CPAN/

Turkey
                      http://ftp.ulak.net.tr/perl/CPAN/
                      ftp://ftp.ulak.net.tr/perl/CPAN
                      ftp://sunsite.bilkent.edu.tr/pub/languages/CPAN/

Ukraine
                      http://cpan.org.ua/
                      ftp://cpan.org.ua/
                      ftp://ftp.perl.org.ua/pub/CPAN/
                      http://no-more.kiev.ua/CPAN/
                      ftp://no-more.kiev.ua/pub/CPAN/

United Kingdom
                      http://www.mirror.ac.uk/sites/ftp.funet.fi/pub/languages/perl/CPAN
                      ftp://ftp.mirror.ac.uk/sites/ftp.funet.fi/pub/languages/perl/CPAN/
                      http://cpan.teleglobe.net/
                      ftp://cpan.teleglobe.net/pub/CPAN
                      http://cpan.mirror.anlx.net/
                      ftp://ftp.mirror.anlx.net/CPAN/
                      http://cpan.etla.org/
                      ftp://cpan.etla.org/pub/CPAN
                      ftp://ftp.demon.co.uk/pub/CPAN/
                      http://cpan.m.flirble.org/
                      ftp://ftp.flirble.org/pub/languages/perl/CPAN/
                      ftp://ftp.plig.org/pub/CPAN/
                      http://cpan.hambule.co.uk/
                      http://cpan.mirrors.clockerz.net/
                      ftp://ftp.clockerz.net/pub/CPAN/
                      ftp://usit.shef.ac.uk/pub/packages/CPAN/

 

North America

Canada
Alberta
                      http://cpan.sunsite.ualberta.ca/
                      ftp://cpan.sunsite.ualberta.ca/pub/CPAN/

Manitoba
                      http://theoryx5.uwinnipeg.ca/pub/CPAN/
                      ftp://theoryx5.uwinnipeg.ca/pub/CPAN/

Nova Scotia
                      ftp://cpan.chebucto.ns.ca/pub/CPAN/

Ontario
                      ftp://ftp.nrc.ca/pub/CPAN/

Mexico
                      http://cpan.azc.uam.mx
                      ftp://cpan.azc.uam.mx/mirrors/CPAN
                      http://www.cpan.unam.mx/
                      ftp://ftp.unam.mx/pub/CPAN
                      http://www.msg.com.mx/CPAN/
                      ftp://ftp.msg.com.mx/pub/CPAN/

United States
Alabama
                      http://mirror.hiwaay.net/CPAN/
                      ftp://mirror.hiwaay.net/CPAN/

California
                      http://cpan.develooper.com/
                      http://www.cpan.org/
                      ftp://cpan.valueclick.com/pub/CPAN/
                      http://www.mednor.net/ftp/pub/mirrors/CPAN/
                      ftp://ftp.mednor.net/pub/mirrors/CPAN/
                      http://mirrors.gossamer-threads.com/CPAN
                      ftp://cpan.nas.nasa.gov/pub/perl/CPAN/
                      http://mirrors.kernel.org/cpan/
                      ftp://mirrors.kernel.org/pub/CPAN
                      http://cpan-sj.viaverio.com/
                      ftp://cpan-sj.viaverio.com/pub/CPAN/
                      http://cpan.digisle.net/
                      ftp://cpan.digisle.net/pub/CPAN
                      http://www.perl.com/CPAN/
                      http://www.uberlan.net/CPAN

Colorado
                      ftp://ftp.cs.colorado.edu/pub/perl/CPAN/
                      http://cpan.four10.com

Delaware
                      http://ftp.lug.udel.edu/pub/CPAN
                      ftp://ftp.lug.udel.edu/pub/CPAN

District of Columbia
                      ftp://ftp.dc.aleron.net/pub/CPAN/

Florida
                      ftp://ftp.cise.ufl.edu/pub/mirrors/CPAN/
                      http://mirror.csit.fsu.edu/pub/CPAN/
                      ftp://mirror.csit.fsu.edu/pub/CPAN/
                      http://cpan.mirrors.nks.net/

Indiana
                      ftp://ftp.uwsg.iu.edu/pub/perl/CPAN/
                      http://cpan.netnitco.net/
                      ftp://cpan.netnitco.net/pub/mirrors/CPAN/
                      http://archive.progeny.com/CPAN/
                      ftp://archive.progeny.com/CPAN/
                      http://fx.saintjoe.edu/pub/CPAN
                      ftp://ftp.saintjoe.edu/pub/CPAN
                      http://csociety-ftp.ecn.purdue.edu/pub/CPAN
                      ftp://csociety-ftp.ecn.purdue.edu/pub/CPAN

Kentucky
                      http://cpan.uky.edu/
                      ftp://cpan.uky.edu/pub/CPAN/
                      http://slugsite.louisville.edu/cpan
                      ftp://slugsite.louisville.edu/CPAN

Massachusetts
                      http://mirrors.towardex.com/CPAN
                      ftp://mirrors.towardex.com/pub/CPAN
                      ftp://ftp.ccs.neu.edu/net/mirrors/ftp.funet.fi/pub/languages/perl/CPAN/

Michigan
                      ftp://cpan.cse.msu.edu/
                      http://cpan.calvin.edu/pub/CPAN
                      ftp://cpan.calvin.edu/pub/CPAN

Nevada
                      http://www.oss.redundant.com/pub/CPAN
                      ftp://www.oss.redundant.com/pub/CPAN

New Jersey
                      http://ftp.cpanel.net/pub/CPAN/
                      ftp://ftp.cpanel.net/pub/CPAN/
                      http://cpan.teleglobe.net/
                      ftp://cpan.teleglobe.net/pub/CPAN

New York
                      http://cpan.belfry.net/
                      http://cpan.erlbaum.net/
                      ftp://cpan.erlbaum.net/
                      http://cpan.thepirtgroup.com/
                      ftp://cpan.thepirtgroup.com/
                      ftp://ftp.stealth.net/pub/CPAN/
                      http://www.rge.com/pub/languages/perl/
                      ftp://ftp.rge.com/pub/languages/perl/

North Carolina
                      http://www.ibiblio.org/pub/languages/perl/CPAN
                      ftp://ftp.ibiblio.org/pub/languages/perl/CPAN
                      ftp://ftp.duke.edu/pub/perl/
                      ftp://ftp.ncsu.edu/pub/mirror/CPAN/

Oklahoma
                      ftp://ftp.ou.edu/mirrors/CPAN/

Oregon
                      ftp://ftp.orst.edu/pub/CPAN

Pennsylvania
                      http://ftp.epix.net/CPAN/
                      ftp://ftp.epix.net/pub/languages/perl/
                      http://mirrors.phenominet.com/pub/CPAN/
                      ftp://mirrors.phenominet.com/pub/CPAN/
                      http://cpan.pair.com/
                      ftp://cpan.pair.com/pub/CPAN/
                      ftp://carroll.cac.psu.edu/pub/CPAN/

Tennessee
                      ftp://ftp.sunsite.utk.edu/pub/CPAN/

Texas
                      http://ftp.sedl.org/pub/mirrors/CPAN/
                      http://www.binarycode.org/cpan
                      ftp://mirror.telentente.com/pub/CPAN
                      http://mirrors.theonlinerecordstore.com/CPAN

Utah
                      ftp://mirror.xmission.com/CPAN/

Virginia
                      http://cpan-du.viaverio.com/
                      ftp://cpan-du.viaverio.com/pub/CPAN/
                      http://mirrors.rcn.net/pub/lang/CPAN/
                      ftp://mirrors.rcn.net/pub/lang/CPAN/
                      http://perl.secsup.org/
                      ftp://perl.secsup.org/pub/perl/
                      http://noc.cvaix.com/mirrors/CPAN/

Washington
                      http://cpan.llarian.net/
                      ftp://cpan.llarian.net/pub/CPAN/
                      http://cpan.mirrorcentral.com/
                      ftp://ftp.mirrorcentral.com/pub/CPAN/
                      ftp://ftp-mirror.internap.com/pub/CPAN/

Wisconsin
                      http://mirror.sit.wisc.edu/pub/CPAN/
                      ftp://mirror.sit.wisc.edu/pub/CPAN/
                      http://mirror.aphix.com/CPAN
                      ftp://mirror.aphix.com/pub/CPAN

 

Oceania

Australia
                      http://ftp.planetmirror.com/pub/CPAN/
                      ftp://ftp.planetmirror.com/pub/CPAN/
                      ftp://mirror.aarnet.edu.au/pub/perl/CPAN/
                      ftp://cpan.topend.com.au/pub/CPAN/
                      http://cpan.mirrors.ilisys.com.au

New Zealand
                      ftp://ftp.auckland.ac.nz/pub/perl/CPAN/

United States
                      http://aniani.ifa.hawaii.edu/CPAN/
                      ftp://aniani.ifa.hawaii.edu/CPAN/

 

South America

Argentina
                      ftp://mirrors.bannerlandia.com.ar/mirrors/CPAN/
                      http://www.linux.org.ar/mirrors/cpan
                      ftp://ftp.linux.org.ar/mirrors/cpan

Brazil
                      ftp://cpan.pop-mg.com.br/pub/CPAN/
                      ftp://ftp.matrix.com.br/pub/perl/CPAN/
                      http://cpan.hostsul.com.br/
                      ftp://cpan.hostsul.com.br/

Chile
                      http://cpan.netglobalis.net/
                      ftp://cpan.netglobalis.net/pub/CPAN/

 

RSYNC Mirrors

                      www.linux.org.ar::cpan
                      theoryx5.uwinnipeg.ca::CPAN
                      ftp.shellhung.org::CPAN
                      rsync.nic.funet.fi::CPAN
                      ftp.u-paris10.fr::CPAN
                      mir1.ovh.net::CPAN
                      rsync://ftp.crihan.fr::CPAN
                      ftp.gwdg.de::FTP/languages/perl/CPAN/
                      ftp.leo.org::CPAN
                      ftp.cbn.net.id::CPAN
                      rsync://ftp.heanet.ie/mirrors/ftp.perl.org/pub/CPAN
                      ftp.iglu.org.il::CPAN
                      gusp.dyndns.org::cpan
                      ftp.kddlabs.co.jp::cpan
                      ftp.ayamura.org::pub/CPAN/
                      mirror.leafbug.org::CPAN
                      rsync.en.com.sg::CPAN
                      mirror.averse.net::cpan
                      rsync.oss.eznetsols.org
                      ftp.kr.FreeBSD.org::CPAN
                      ftp.solnet.ch::CPAN
                      cpan.cdpa.nsysu.edu.tw::CPAN
                      cpan.teleglobe.net::CPAN
                      rsync://rsync.mirror.anlx.net::CPAN
                      ftp.sedl.org::cpan
                      ibiblio.org::CPAN
                      cpan-du.viaverio.com::CPAN
                      aniani.ifa.hawaii.edu::CPAN
                      archive.progeny.com::CPAN
                      rsync://slugsite.louisville.edu::CPAN
                      mirror.aphix.com::CPAN
                      cpan.teleglobe.net::CPAN
                      ftp.lug.udel.edu::cpan
                      mirrors.kernel.org::mirrors/CPAN
                      mirrors.phenominet.com::CPAN
                      cpan.pair.com::CPAN
                      cpan-sj.viaverio.com::CPAN
                      mirror.csit.fsu.edu::CPAN
                      csociety-ftp.ecn.purdue.edu::CPAN

For an up-to-date listing of CPAN sites, see http://www.cpan.org/SITES or ftp://www.cpan.org/SITES .  

Modules: Creation, Use, and Abuse

(The following section is borrowed directly from Tim Bunce's modules file, available at your nearest CPAN site.)

Perl implements a class using a package, but the presence of a package doesn't imply the presence of a class. A package is just a namespace. A class is a package that provides subroutines that can be used as methods. A method is just a subroutine that expects, as its first argument, either the name of a package (for ``static'' methods), or a reference to something (for ``virtual'' methods).

A module is a file that (by convention) provides a class of the same name (sans the .pm), plus an import method in that class that can be called to fetch exported symbols. This module may implement some of its methods by loading dynamic C or C++ objects, but that should be totally transparent to the user of the module. Likewise, the module might set up an AUTOLOAD function to slurp in subroutine definitions on demand, but this is also transparent. Only the .pm file is required to exist. See perlsub, perltoot, and AutoLoader for details about the AUTOLOAD mechanism.  

Guidelines for Module Creation

*
Do similar modules already exist in some form?

If so, please try to reuse the existing modules either in whole or by inheriting useful features into a new class. If this is not practical try to get together with the module authors to work on extending or enhancing the functionality of the existing modules. A perfect example is the plethora of packages in perl4 for dealing with command line options.

If you are writing a module to expand an already existing set of modules, please coordinate with the author of the package. It helps if you follow the same naming scheme and module interaction scheme as the original author.

*
Try to design the new module to be easy to extend and reuse.

Try to "use warnings;" (or "use warnings qw(...);"). Remember that you can add "no warnings qw(...);" to individual blocks of code that need less warnings.

Use blessed references. Use the two argument form of bless to bless into the class name given as the first parameter of the constructor, e.g.,:

 sub new {
     my $class = shift;
     return bless {}, $class;
 }

or even this if you'd like it to be used as either a static or a virtual method.

 sub new {
     my $self  = shift;
     my $class = ref($self) || $self;
     return bless {}, $class;
 }

Pass arrays as references so more parameters can be added later (it's also faster). Convert functions into methods where appropriate. Split large methods into smaller more flexible ones. Inherit methods from other modules if appropriate.

Avoid class name tests like: "die "Invalid" unless ref $ref eq 'FOO'". Generally you can delete the "eq 'FOO'" part with no harm at all. Let the objects look after themselves! Generally, avoid hard-wired class names as far as possible.

Avoid "$r->Class::func()" where using "@ISA=qw(... Class ...)" and "$r->func()" would work (see perlbot for more details).

Use autosplit so little used or newly added functions won't be a burden to programs that don't use them. Add test functions to the module after __END__ either using AutoSplit or by saying:

 eval join('',<main::DATA>) || die $@ unless caller();

Does your module pass the 'empty subclass' test? If you say "@SUBCLASS::ISA = qw(YOURCLASS);" your applications should be able to use SUBCLASS in exactly the same way as YOURCLASS. For example, does your application still work if you change: "$obj = new YOURCLASS;" into: "$obj = new SUBCLASS;" ?

Avoid keeping any state information in your packages. It makes it difficult for multiple other packages to use yours. Keep state information in objects.

Always use -w.

Try to "use strict;" (or "use strict qw(...);"). Remember that you can add "no strict qw(...);" to individual blocks of code that need less strictness.

Always use -w.

Follow the guidelines in the perlstyle(1) manual.

Always use -w.

*
Some simple style guidelines

The perlstyle manual supplied with Perl has many helpful points.

Coding style is a matter of personal taste. Many people evolve their style over several years as they learn what helps them write and maintain good code. Here's one set of assorted suggestions that seem to be widely used by experienced developers:

Use underscores to separate words. It is generally easier to read $var_names_like_this than $VarNamesLikeThis, especially for non-native speakers of English. It's also a simple rule that works consistently with VAR_NAMES_LIKE_THIS.

Package/Module names are an exception to this rule. Perl informally reserves lowercase module names for 'pragma' modules like integer and strict. Other modules normally begin with a capital letter and use mixed case with no underscores (need to be short and portable).

You may find it helpful to use letter case to indicate the scope or nature of a variable. For example:

 $ALL_CAPS_HERE   constants only (beware clashes with Perl vars)
 $Some_Caps_Here  package-wide global/static
 $no_caps_here    function scope my() or local() variables

Function and method names seem to work best as all lowercase. e.g., "$obj->as_string()".

You can use a leading underscore to indicate that a variable or function should not be used outside the package that defined it.

*
Select what to export.

Do NOT export method names!

Do NOT export anything else by default without a good reason!

Exports pollute the namespace of the module user. If you must export try to use @EXPORT_OK in preference to @EXPORT and avoid short or common names to reduce the risk of name clashes.

Generally anything not exported is still accessible from outside the module using the ModuleName::item_name (or "$blessed_ref->method") syntax. By convention you can use a leading underscore on names to indicate informally that they are 'internal' and not for public use.

(It is actually possible to get private functions by saying: "my $subref = sub { ... }; &$subref;". But there's no way to call that directly as a method, because a method must have a name in the symbol table.)

As a general rule, if the module is trying to be object oriented then export nothing. If it's just a collection of functions then @EXPORT_OK anything but use @EXPORT with caution.

*
Select a name for the module.

This name should be as descriptive, accurate, and complete as possible. Avoid any risk of ambiguity. Always try to use two or more whole words. Generally the name should reflect what is special about what the module does rather than how it does it. Please use nested module names to group informally or categorize a module. There should be a very good reason for a module not to have a nested name. Module names should begin with a capital letter.

Having 57 modules all called Sort will not make life easy for anyone (though having 23 called Sort::Quick is only marginally better :-). Imagine someone trying to install your module alongside many others. If in any doubt ask for suggestions in comp.lang.perl.misc.

If you are developing a suite of related modules/classes it's good practice to use nested classes with a common prefix as this will avoid namespace clashes. For example: Xyz::Control, Xyz::View, Xyz::Model etc. Use the modules in this list as a naming guide.

If adding a new module to a set, follow the original author's standards for naming modules and the interface to methods in those modules.

If developing modules for private internal or project specific use, that will never be released to the public, then you should ensure that their names will not clash with any future public module. You can do this either by using the reserved Local::* category or by using a category name that includes an underscore like Foo_Corp::*.

To be portable each component of a module name should be limited to 11 characters. If it might be used on MS-DOS then try to ensure each is unique in the first 8 characters. Nested modules make this easier.

*
Have you got it right?

How do you know that you've made the right decisions? Have you picked an interface design that will cause problems later? Have you picked the most appropriate name? Do you have any questions?

The best way to know for sure, and pick up many helpful suggestions, is to ask someone who knows. Comp.lang.perl.misc is read by just about all the people who develop modules and it's the best place to ask.

All you need to do is post a short summary of the module, its purpose and interfaces. A few lines on each of the main methods is probably enough. (If you post the whole module it might be ignored by busy people - generally the very people you want to read it!)

Don't worry about posting if you can't say when the module will be ready - just say so in the message. It might be worth inviting others to help you, they may be able to complete it for you!

*
README and other Additional Files.

It's well known that software developers usually fully document the software they write. If, however, the world is in urgent need of your software and there is not enough time to write the full documentation please at least provide a README file containing:

*
A description of the module/package/extension etc.
*
A copyright notice - see below.
*
Prerequisites - what else you may need to have.
*
How to build it - possible changes to Makefile.PL etc.
*
How to install it.
*
Recent changes in this release, especially incompatibilities
*
Changes / enhancements you plan to make in the future.

If the README file seems to be getting too large you may wish to split out some of the sections into separate files: INSTALL, Copying, ToDo etc.

*
Adding a Copyright Notice.

How you choose to license your work is a personal decision. The general mechanism is to assert your Copyright and then make a declaration of how others may copy/use/modify your work.

Perl, for example, is supplied with two types of licence: The GNU GPL and The Artistic Licence (see the files README, Copying, and Artistic, or perlgpl and perlartistic). Larry has good reasons for NOT just using the GNU GPL.

My personal recommendation, out of respect for Larry, Perl, and the Perl community at large is to state something simply like:

 Copyright (c) 1995 Your Name. All rights reserved.
 This program is free software; you can redistribute it and/or
 modify it under the same terms as Perl itself.

This statement should at least appear in the README file. You may also wish to include it in a Copying file and your source files. Remember to include the other words in addition to the Copyright.

*
Give the module a version/issue/release number.

To be fully compatible with the Exporter and MakeMaker modules you should store your module's version number in a non-my package variable called $VERSION. This should be a floating point number with at least two digits after the decimal (i.e., hundredths, e.g, "$VERSION = "0.01""). Don't use a ``1.3.2'' style version. See Exporter for details.

It may be handy to add a function or method to retrieve the number. Use the number in announcements and archive file names when releasing the module (ModuleName-1.02.tar.Z). See perldoc ExtUtils::MakeMaker.pm for details.

*
How to release and distribute a module.

It's good idea to post an announcement of the availability of your module (or the module itself if small) to the comp.lang.perl.announce Usenet newsgroup. This will at least ensure very wide once-off distribution.

If possible, register the module with CPAN. You should include details of its location in your announcement.

Some notes about ftp archives: Please use a long descriptive file name that includes the version number. Most incoming directories will not be readable/listable, i.e., you won't be able to see your file after uploading it. Remember to send your email notification message as soon as possible after uploading else your file may get deleted automatically. Allow time for the file to be processed and/or check the file has been processed before announcing its location.

FTP Archives for Perl Modules:

Follow the instructions and links on:

   http://www.cpan.org/modules/00modlist.long.html
   http://www.cpan.org/modules/04pause.html

or upload to one of these sites:

   https://pause.kbx.de/pause/
   http://pause.perl.org/pause/

and notify <modules@perl.org>.

By using the WWW interface you can ask the Upload Server to mirror your modules from your ftp or WWW site into your own directory on CPAN!

Please remember to send me an updated entry for the Module list!

*
Take care when changing a released module.

Always strive to remain compatible with previous released versions. Otherwise try to add a mechanism to revert to the old behavior if people rely on it. Document incompatible changes.

 

Guidelines for Converting Perl 4 Library Scripts into Modules

*
There is no requirement to convert anything.

If it ain't broke, don't fix it! Perl 4 library scripts should continue to work with no problems. You may need to make some minor changes (like escaping non-array @'s in double quoted strings) but there is no need to convert a .pl file into a Module for just that.

*
Consider the implications.

All Perl applications that make use of the script will need to be changed (slightly) if the script is converted into a module. Is it worth it unless you plan to make other changes at the same time?

*
Make the most of the opportunity.

If you are going to convert the script to a module you can use the opportunity to redesign the interface. The guidelines for module creation above include many of the issues you should consider.

*
The pl2pm utility will get you started.

This utility will read *.pl files (given as parameters) and write corresponding *.pm files. The pl2pm utilities does the following:

*
Adds the standard Module prologue lines
*
Converts package specifiers from ' to ::
*
Converts die(...) to croak(...)
*
Several other minor changes

Being a mechanical process pl2pm is not bullet proof. The converted code will need careful checking, especially any package statements. Don't delete the original .pl file till the new .pm one works!

 

Guidelines for Reusing Application Code

*
Complete applications rarely belong in the Perl Module Library.
*
Many applications contain some Perl code that could be reused.

Help save the world! Share your code in a form that makes it easy to reuse.

*
Break-out the reusable code into one or more separate module files.
*
Take the opportunity to reconsider and redesign the interfaces.
*
In some cases the 'application' can then be reduced to a small

fragment of code built on top of the reusable modules. In these cases the application could invoked as:

     % perl -e 'use Module::Name; method(@ARGV)' ...
or
     % perl -mModule::Name ...    (in perl5.002 or higher)

 

NOTE

Perl does not enforce private and public parts of its modules as you may have been used to in other languages like C++, Ada, or Modula-17. Perl doesn't have an infatuation with enforced privacy. It would prefer that you stayed out of its living room because you weren't invited, not because it has a shotgun.

The module and its user have a contract, part of which is common law, and part of which is ``written''. Part of the common law contract is that a module doesn't pollute any namespace it wasn't asked to. The written contract for the module (A.K.A. documentation) may make other provisions. But then you know when you "use RedefineTheWorld" that you're redefining the world and willing to take the consequences.


 

Index

NAME
THE PERL MODULE LIBRARY
Pragmatic Modules
Standard Modules
Extension Modules
CPAN
Africa
Asia
Central America
Europe
North America
Oceania
South America
RSYNC Mirrors
Modules: Creation, Use, and Abuse
Guidelines for Module Creation
Guidelines for Converting Perl 4 Library Scripts into Modules
Guidelines for Reusing Application Code
NOTE




Random Man Pages:
shadebobs
fun
bzgrep
slabinfo