perlmodlib - constructing new Perl modules and finding existing ones

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

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 class 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
Carp: Warn of errors (from perspective of caller)
Carp::Heavy: 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
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
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::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_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: Methods to override UN*X behaviour in ExtUtils::MakeMaker
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_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_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::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: Split a pathname into pieces
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::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 math package
Math::BigInt::Calc: Pure Perl module to support Math::BigInt
Math::BigRat: Arbitrarily big rationals
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::Harness: Run Perl standard test scripts with statistics
Test::Harness::Assert: Simple assert
Test::Harness::Iterator: Internal Test::Harness Iterator
Test::Harness::Straps: Detailed analysis of test results
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
Win32: Interfaces to some Win32 API 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 the perl manpage 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:

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

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 the perlsub manpage, the perltoot manpage, and the AutoLoader manpage for details about the AUTOLOAD mechanism.

Guidelines for Module Creation

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 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 the perlbot manpage 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.

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.

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.

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.

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!

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:

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.

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 the perlgpl manpage and the perlartistic manpage). 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.

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 the Exporter manpage 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.

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!

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

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.

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?

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.

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

die(...)

croak(...)

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

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

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.

perlmodlib - constructing new Perl modules and finding existing ones