Perl 5 version 12.0 documentation

perlmodlib

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:

  1. no integer;
  2. no strict 'refs';
  3. 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).

    12
    attributes

    Get/set subroutine or variable attributes

    12
    autouse

    Postpone load of modules until a function is used

    12
    blib

    Use MakeMaker's uninstalled version of a package

    12
    bytes

    Force byte semantics rather than character semantics

    12
    charnames

    Define character names for \N{named} string literal escapes

    12
    deprecate

    Perl pragma for deprecating the core version of a module

    12
    diagnostics

    Produce verbose warning diagnostics

    12
    feature

    Enable new features

    12
    filetest

    Control the filetest permission operators

    12
    integer

    Use integer arithmetic instead of floating point

    12
    less

    Request less of something

    12
    locale

    Use and avoid POSIX locales for built-in operations

    12
    mro

    Method Resolution Order

    12
    open

    Set default PerlIO layers for input and output

    12
    ops

    Restrict unsafe operations when compiling

    12
    overload

    Package for overloading Perl operations

    12
    overloading

    Lexically control overloading

    12
    re

    Alter regular expression behaviour

    12
    sigtrap

    Enable simple signal handling

    12
    sort

    Control sort() behaviour

    12
    strict

    Restrict unsafe constructs

    12
    subs

    Predeclare sub names

    12
    utf8

    Enable/disable UTF-8 (or UTF-EBCDIC) in source code

    12
    vars

    Predeclare global variable names (obsolete)

    12
    version

    Perl extension for Version Objects

    12
    vmsish

    Control VMS-specific language features

    12
    warnings

    Control optional warnings

    12
    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.

    12
    AnyDBM_File

    Provide framework for multiple DBMs

    12
    B

    The Perl Compiler Backend

    12
    B::Concise

    Walk Perl syntax tree, printing concise info about ops

    12
    B::Showlex

    Show lexical variables used in functions or files

    12
    B::Terse

    Walk Perl syntax tree, printing terse info about ops

    12
    B::Xref

    Generates cross reference reports for Perl programs

    12
    Benchmark

    Benchmark running times of Perl code

    12
    CORE

    Pseudo-namespace for Perl's core routines

    12
    Carp

    Warn of errors (from perspective of caller)

    12
    Class::Struct

    Declare struct-like datatypes as Perl classes

    12
    Config

    Access Perl configuration information

    12
    DB

    Programmatic interface to the Perl debugging API

    12
    DBM_Filter

    Filter DBM keys/values

    12
    DBM_Filter::compress

    Filter for DBM_Filter

    12
    DBM_Filter::encode

    Filter for DBM_Filter

    12
    DBM_Filter::int32

    Filter for DBM_Filter

    12
    DBM_Filter::null

    Filter for DBM_Filter

    12
    DBM_Filter::utf8

    Filter for DBM_Filter

    12
    Devel::DProf

    A Perl code profiler

    12
    Devel::Peek

    A data debugging tool for the XS programmer

    12
    Devel::SelfStubber

    Generate stubs for a SelfLoading module

    12
    DirHandle

    Supply object methods for directory handles

    12
    Dumpvalue

    Provides screen dump of Perl data.

    12
    DynaLoader

    Dynamically load C libraries into Perl code

    12
    English

    Use nice English (or awk) names for ugly punctuation variables

    12
    Env

    Perl module that imports environment variables as scalars or arrays

    12
    Errno

    System errno constants

    12
    Exporter

    Implements default import method for modules

    12
    Exporter::Heavy

    Exporter guts

    12
    ExtUtils::Embed

    Utilities for embedding Perl in C/C++ applications

    12
    ExtUtils::XSSymSet

    Keep sets of symbol names palatable to the VMS linker

    12
    Fcntl

    Load the C Fcntl.h defines

    12
    File::Basename

    Parse file paths into directory, filename and suffix.

    12
    File::CheckTree

    Run many filetest checks on a tree

    12
    File::Compare

    Compare files or filehandles

    12
    File::Copy

    Copy files or filehandles

    12
    File::DosGlob

    DOS like globbing and then some

    12
    File::Find

    Traverse a directory tree.

    12
    File::Glob

    Perl extension for BSD glob routine

    12
    File::stat

    By-name interface to Perl's built-in stat() functions

    12
    FileCache

    Keep more files open than the system permits

    12
    FileHandle

    Supply object methods for filehandles

    12
    FindBin

    Locate directory of original perl script

    12
    GDBM_File

    Perl5 access to the gdbm library.

    12
    Getopt::Std

    Process single-character switches with switch clustering

    12
    Hash::Util

    A selection of general-utility hash subroutines

    12
    Hash::Util::FieldHash

    Support for Inside-Out Classes

    12
    I18N::Collate

    Compare 8-bit scalar data according to the current locale

    12
    I18N::Langinfo

    Query locale information

    12
    IPC::Open2

    Open a process for both reading and writing using open2()

    12
    IPC::Open3

    Open a process for reading, writing, and error handling using open3()

    12
    NDBM_File

    Tied access to ndbm files

    12
    Net::hostent

    By-name interface to Perl's built-in gethost*() functions

    12
    Net::netent

    By-name interface to Perl's built-in getnet*() functions

    12
    Net::protoent

    By-name interface to Perl's built-in getproto*() functions

    12
    Net::servent

    By-name interface to Perl's built-in getserv*() functions

    12
    O

    Generic interface to Perl Compiler backends

    12
    ODBM_File

    Tied access to odbm files

    12
    Opcode

    Disable named opcodes when compiling perl code

    12
    POSIX

    Perl interface to IEEE Std 1003.1

    12
    PerlIO

    On demand loader for PerlIO layers and root of PerlIO::* name space

    12
    PerlIO::encoding

    Encoding layer

    12
    PerlIO::scalar

    In-memory IO, scalar IO

    12
    PerlIO::via

    Helper class for PerlIO layers implemented in perl

    12
    Pod::Functions

    Group Perl's functions a la perlfunc.pod

    12
    Pod::Html

    Module to convert pod files to HTML

    12
    SDBM_File

    Tied access to sdbm files

    12
    Search::Dict

    Search for key in dictionary file

    12
    SelectSaver

    Save and restore selected file handle

    12
    Socket

    Load the C socket.h defines and structure manipulators

    12
    Symbol

    Manipulate Perl symbols and their names

    12
    Sys::Hostname

    Try every conceivable way to get hostname

    12
    Term::Complete

    Perl word completion module

    12
    Term::ReadLine

    Perl interface to various readline packages.

    12
    Text::Abbrev

    Create an abbreviation table from a list

    12
    Thread

    Manipulate threads in Perl (for old code only)

    12
    Tie::Array

    Base class for tied arrays

    12
    Tie::Handle

    Base class definitions for tied handles

    12
    Tie::Hash

    Base class definitions for tied hashes

    12
    Tie::Hash::NamedCapture

    Named regexp capture buffers

    12
    Tie::Memoize

    Add data to hash when needed

    12
    Tie::Scalar

    Base class definitions for tied scalars

    12
    Tie::StdHandle

    Base class definitions for tied handles

    12
    Tie::SubstrHash

    Fixed-table-size, fixed-key-length hashing

    12
    Time::Local

    Efficiently compute time from local and GMT time

    12
    Time::gmtime

    By-name interface to Perl's built-in gmtime() function

    12
    Time::localtime

    By-name interface to Perl's built-in localtime() function

    12
    Time::tm

    Internal object used by Time::gmtime and Time::localtime

    12
    UNIVERSAL

    Base class for ALL classes (blessed references)

    12
    Unicode::UCD

    Unicode character database

    12
    User::grent

    By-name interface to Perl's built-in getgr*() functions

    12
    User::pwent

    By-name interface to Perl's built-in getpw*() functions

    12
    VMS::DCLsym

    Perl extension to manipulate DCL symbols

    12
    VMS::Stdio

    Standard I/O functions via VMS extensions

    12
    Win32CORE

    Win32 CORE function stubs

    12
    XS::APItest

    Test the perl C API

    12
    XS::APItest::KeywordRPN

    Write arithmetic expressions in RPN

    12
    XS::Typemap

    Module to test the XS typemaps distributed with perl

    12
    version::Internals

    Perl extension for Version Objects

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).

  1. % perl -MFile::Find=find -MFile::Spec::Functions -Tlwe \
  2. 'find { wanted => sub { print canonpath $_ if /\.pm\z/ },
  3. 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 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.

Registered CPAN sites

Africa

    12
    South Africa
    1. http://cpan.mirror.ac.za/
    2. ftp://cpan.mirror.ac.za/
    3. http://mirror.is.co.za/pub/cpan/
    4. ftp://ftp.is.co.za/pub/cpan/
    5. ftp://ftp.saix.net/pub/CPAN/

Asia

    12
    Hong Kong
    1. http://ftp.cuhk.edu.hk/pub/packages/perl/CPAN/
    2. ftp://ftp.cuhk.edu.hk/pub/packages/perl/CPAN/
    3. http://mirrors.geoexpat.com/cpan/
    12
    India
    1. http://perlmirror.indialinks.com/
    12
    Indonesia
    1. http://cpan.biz.net.id/
    2. http://komo.vlsm.org/CPAN/
    3. ftp://komo.vlsm.org/CPAN/
    4. http://cpan.pesat.net.id/
    5. http://mirror.unej.ac.id/cpan/
    6. ftp://mirror.unej.ac.id/cpan/
    12
    Japan
    1. ftp://ftp.u-aizu.ac.jp/pub/CPAN
    2. ftp://ftp.kddilabs.jp/CPAN/
    3. http://ftp.nara.wide.ad.jp/pub/CPAN/
    4. ftp://ftp.nara.wide.ad.jp/pub/CPAN/
    5. http://ftp.jaist.ac.jp/pub/CPAN/
    6. ftp://ftp.jaist.ac.jp/pub/CPAN/
    7. ftp://ftp.dti.ad.jp/pub/lang/CPAN/
    8. ftp://ftp.ring.gr.jp/pub/lang/perl/CPAN/
    9. http://ftp.riken.jp/lang/CPAN/
    10. ftp://ftp.riken.jp/lang/CPAN/
    11. http://ftp.yz.yamagata-u.ac.jp/pub/lang/cpan/
    12. ftp://ftp.yz.yamagata-u.ac.jp/pub/lang/cpan/
    12
    Kazakhstan
    1. http://mirror.linuxiso.kz/CPAN/
    12
    Republic of Korea
    1. http://ftp.kaist.ac.kr/pub/CPAN
    2. ftp://ftp.kaist.ac.kr/pub/CPAN
    3. http://cpan.mirror.cdnetworks.com/
    4. ftp://cpan.mirror.cdnetworks.com/CPAN/
    5. http://cpan.sarang.net/
    6. ftp://cpan.sarang.net/CPAN/
    12
    Russia
    1. http://cpan.tomsk.ru/
    2. ftp://cpan.tomsk.ru/
    12
    Singapore
    1. http://mirror.averse.net/pub/CPAN
    2. ftp://mirror.averse.net/pub/CPAN
    3. http://cpan.mirror.choon.net/
    4. http://cpan.oss.eznetsols.org
    5. ftp://ftp.oss.eznetsols.org/cpan
    12
    Taiwan
    1. http://ftp.cse.yzu.edu.tw/pub/CPAN/
    2. ftp://ftp.cse.yzu.edu.tw/pub/CPAN/
    3. http://cpan.nctu.edu.tw/
    4. ftp://cpan.nctu.edu.tw/
    5. ftp://ftp.ncu.edu.tw/CPAN/
    6. http://cpan.cdpa.nsysu.edu.tw/
    7. ftp://cpan.cdpa.nsysu.edu.tw/Unix/Lang/CPAN/
    8. http://cpan.stu.edu.tw
    9. ftp://ftp.stu.edu.tw/CPAN
    10. http://ftp.stu.edu.tw/CPAN
    11. ftp://ftp.stu.edu.tw/pub/CPAN
    12. http://cpan.cs.pu.edu.tw/
    13. ftp://cpan.cs.pu.edu.tw/pub/CPAN
    12
    Thailand
    1. http://mirrors.issp.co.th/cpan/
    2. ftp://mirrors.issp.co.th/cpan/
    12
    Turkey
    1. http://cpan.gazi.edu.tr/
    2. http://cpan.ulak.net.tr
    3. ftp://ftp.ulak.net.tr/pub/CPAN
    12
    Viet Nam
    1. http://mirror-fpt-telecom.fpt.net/cpan/
    2. ftp://mirror-fpt-telecom.fpt.net/cpan/

Central America

    12
    Costa Rica
    1. http://mirrors.ucr.ac.cr/CPAN/
    2. ftp://mirrors.ucr.ac.cr/CPAN/

Europe

    12
    Austria
    1. http://cpan.inode.at/
    2. ftp://cpan.inode.at
    3. http://gd.tuwien.ac.at/languages/perl/CPAN/
    4. ftp://gd.tuwien.ac.at/pub/CPAN/
    12
    Belgium
    1. http://ftp.belnet.be/mirror/ftp.cpan.org/
    2. ftp://ftp.belnet.be/mirror/ftp.cpan.org/
    3. http://ftp.easynet.be/pub/CPAN/
    4. http://cpan.weepee.org/
    5. http://cpan.fluoline.net/
    12
    Bosnia and Herzegovina
    1. http://cpan.blic.net/
    12
    Bulgaria
    1. http://cpan.cbox.biz/
    2. ftp://cpan.cbox.biz/cpan/
    3. http://cpan.digsys.bg/
    4. ftp://ftp.digsys.bg/pub/CPAN
    12
    Croatia
    1. http://ftp.carnet.hr/pub/CPAN/
    2. ftp://ftp.carnet.hr/pub/CPAN/
    12
    Czech Republic
    1. ftp://ftp.fi.muni.cz/pub/CPAN/
    2. http://archive.cpan.cz/
    12
    Denmark
    1. http://mirrors.dotsrc.org/cpan
    2. ftp://mirrors.dotsrc.org/cpan/
    3. http://www.cpan.dk/
    4. http://mirror.uni-c.dk/pub/CPAN/
    12
    Finland
    1. ftp://ftp.funet.fi/pub/languages/perl/CPAN/
    2. http://mirror.eunet.fi/CPAN
    12
    France
    1. http://cpan.enstimac.fr/
    2. ftp://ftp.inria.fr/pub/CPAN/
    3. http://distrib-coffee.ipsl.jussieu.fr/pub/mirrors/cpan/
    4. ftp://distrib-coffee.ipsl.jussieu.fr/pub/mirrors/cpan/
    5. ftp://ftp.lip6.fr/pub/perl/CPAN/
    6. http://mir2.ovh.net/ftp.cpan.org
    7. ftp://mir1.ovh.net/ftp.cpan.org
    8. http://cpan.miroir-francais.fr/
    9. ftp://miroir-francais.fr/pub/cpan/
    10. ftp://ftp.oleane.net/pub/CPAN/
    11. http://ftp.crihan.fr/mirrors/ftp.cpan.org/
    12. ftp://ftp.crihan.fr/mirrors/ftp.cpan.org/
    13. http://ftp.u-strasbg.fr/CPAN
    14. ftp://ftp.u-strasbg.fr/CPAN
    15. http://cpan.cict.fr/
    16. ftp://cpan.cict.fr/pub/CPAN/
    12
    Germany
    1. ftp://ftp.fu-berlin.de/unix/languages/perl/
    2. http://mirrors.softliste.de/cpan/
    3. ftp://ftp.rub.de/pub/CPAN/
    4. http://www.planet-elektronik.de/CPAN/
    5. http://ftp.hosteurope.de/pub/CPAN/
    6. ftp://ftp.hosteurope.de/pub/CPAN/
    7. http://www.mirrorspace.org/cpan/
    8. http://mirror.netcologne.de/cpan/
    9. ftp://mirror.netcologne.de/cpan/
    10. ftp://ftp.freenet.de/pub/ftp.cpan.org/pub/CPAN/
    11. http://ftp-stud.hs-esslingen.de/pub/Mirrors/CPAN/
    12. ftp://ftp-stud.hs-esslingen.de/pub/Mirrors/CPAN/
    13. http://mirrors.zerg.biz/cpan/
    14. http://ftp.gwdg.de/pub/languages/perl/CPAN/
    15. ftp://ftp.gwdg.de/pub/languages/perl/CPAN/
    16. http://dl.ambiweb.de/mirrors/ftp.cpan.org/
    17. http://cpan.mirror.clusters.kg/
    18. http://cpan.mirror.iphh.net/
    19. ftp://cpan.mirror.iphh.net/pub/CPAN/
    20. http://cpan.mirroring.de/
    21. http://mirror.informatik.uni-mannheim.de/pub/mirrors/CPAN/
    22. ftp://mirror.informatik.uni-mannheim.de/pub/mirrors/CPAN/
    23. http://ftp.cw.net/pub/CPAN/
    24. ftp://ftp.cw.net/pub/CPAN/
    25. http://cpan.cpantesters.org/
    26. ftp://cpan.cpantesters.org/CPAN/
    27. http://cpan.mirrored.de/
    28. ftp://mirror.petamem.com/CPAN/
    29. http://cpan.noris.de/
    30. ftp://cpan.noris.de/pub/CPAN/
    31. ftp://ftp.mpi-sb.mpg.de/pub/perl/CPAN/
    32. ftp://ftp.gmd.de/mirrors/CPAN/
    12
    Greece
    1. ftp://ftp.forthnet.gr/pub/languages/perl/CPAN
    2. ftp://ftp.ntua.gr/pub/lang/perl/
    3. http://cpan.cc.uoc.gr/
    4. ftp://ftp.cc.uoc.gr/mirrors/CPAN/
    12
    Hungary
    1. http://cpan.mirrors.enexis.hu/
    2. ftp://cpan.mirrors.enexis.hu/mirrors/cpan/
    3. http://cpan.hu/
    12
    Iceland
    1. http://ftp.rhnet.is/pub/CPAN/
    2. ftp://ftp.rhnet.is/pub/CPAN/
    12
    Ireland
    1. http://ftp.esat.net/pub/languages/perl/CPAN/
    2. ftp://ftp.esat.net/pub/languages/perl/CPAN/
    3. http://ftp.heanet.ie/mirrors/ftp.perl.org/pub/CPAN
    4. ftp://ftp.heanet.ie/mirrors/ftp.perl.org/pub/CPAN
    12
    Italy
    1. http://bo.mirror.garr.it/mirrors/CPAN/
    2. http://cpan.panu.it/
    3. ftp://ftp.panu.it/pub/mirrors/perl/CPAN/
    4. http://cpan.fastbull.org/
    12
    Latvia
    1. http://kvin.lv/pub/CPAN/
    12
    Lithuania
    1. http://ftp.litnet.lt/pub/CPAN/
    2. ftp://ftp.litnet.lt/pub/CPAN/
    12
    Malta
    1. http://cpan.waldonet.net.mt/
    12
    Netherlands
    1. ftp://ftp.quicknet.nl/pub/CPAN/
    2. http://mirror.hostfuss.com/CPAN/
    3. ftp://mirror.hostfuss.com/CPAN/
    4. http://mirrors3.kernel.org/cpan/
    5. ftp://mirrors3.kernel.org/pub/CPAN/
    6. http://cpan.osmirror.nl/
    7. ftp://ftp.osmirror.nl/pub/cpan/
    8. http://cpan.mirror.versatel.nl/
    9. ftp://ftp.mirror.versatel.nl/cpan/
    10. ftp://download.xs4all.nl/pub/mirror/CPAN/
    11. http://mirror.leaseweb.com/CPAN/
    12. ftp://mirror.leaseweb.com/CPAN/
    13. ftp://ftp.cpan.nl/pub/CPAN/
    14. http://archive.cs.uu.nl/mirror/CPAN/
    15. ftp://ftp.cs.uu.nl/mirror/CPAN/
    16. http://https://luxitude.net/cpan/
    12
    Norway
    1. ftp://ftp.uninett.no/pub/languages/perl/CPAN
    2. ftp://ftp.uit.no/pub/languages/perl/cpan/
    12
    Poland
    1. http://mirror.icis.pcz.pl/CPAN/
    2. ftp://mirror.icis.pcz.pl/CPAN/
    3. http://piotrkosoft.net/pub/mirrors/CPAN/
    4. ftp://ftp.piotrkosoft.net/pub/mirrors/CPAN/
    5. http://ftp.man.poznan.pl/pub/CPAN
    6. ftp://ftp.man.poznan.pl/pub/CPAN
    7. ftp://sunsite.icm.edu.pl/pub/CPAN/
    8. ftp://ftp.tpnet.pl/d4/CPAN/
    12
    Portugal
    1. http://cpan.dei.uc.pt/
    2. ftp://ftp.dei.uc.pt/pub/CPAN
    3. ftp://ftp.ist.utl.pt/pub/CPAN/
    4. http://cpan.perl.pt/
    5. http://cpan.ip.pt/
    6. ftp://cpan.ip.pt/pub/cpan/
    7. http://mirrors.nfsi.pt/CPAN/
    8. ftp://mirrors.nfsi.pt/pub/CPAN/
    9. http://cpan.dcc.fc.up.pt/
    12
    Romania
    1. http://ftp.astral.ro/pub/CPAN/
    2. ftp://ftp.astral.ro/pub/CPAN/
    3. ftp://ftp.lug.ro/CPAN
    4. http://mirrors.xservers.ro/CPAN/
    5. http://mirrors.hostingromania.ro/ftp.cpan.org/
    6. ftp://ftp.hostingromania.ro/mirrors/ftp.cpan.org/
    7. ftp://ftp.iasi.roedu.net/pub/mirrors/ftp.cpan.org/
    8. ftp://ftp.ambra.ro/pub/CPAN
    12
    Russia
    1. ftp://ftp.aha.ru/CPAN/
    2. http://cpan.rinet.ru/
    3. ftp://cpan.rinet.ru/pub/mirror/CPAN/
    4. ftp://ftp.SpringDaemons.com/pub/CPAN/
    5. http://cpan.nx1.ru/
    6. ftp://cpan.nx1.ru/
    7. http://mirror.rol.ru/CPAN/
    8. http://ftp.silvernet.ru/CPAN/
    9. http://ftp.spbu.ru/CPAN/
    10. ftp://ftp.spbu.ru/CPAN/
    12
    Slovakia
    1. http://cpan.fyxm.net/
    12
    Slovenia
    1. http://www.klevze.si/cpan
    12
    Spain
    1. http://osl.ugr.es/CPAN/
    2. ftp://ftp.rediris.es/mirror/CPAN/
    3. http://ftp.gui.uva.es/sites/cpan.org/
    4. ftp://ftp.gui.uva.es/sites/cpan.org/
    12
    Sweden
    1. http://mirrors4.kernel.org/cpan/
    2. ftp://mirrors4.kernel.org/pub/CPAN/
    12
    Switzerland
    1. http://cpan.mirror.solnet.ch/
    2. ftp://ftp.solnet.ch/mirror/CPAN/
    3. http://mirror.switch.ch/ftp/mirror/CPAN/
    4. ftp://mirror.switch.ch/mirror/CPAN/
    12
    Ukraine
    1. http://cpan.makeperl.org/
    2. ftp://cpan.makeperl.org/pub/CPAN
    3. http://cpan.org.ua/
    4. http://no-more.kiev.ua/CPAN/
    5. ftp://no-more.kiev.ua/pub/CPAN/
    6. http://cpan.gafol.net/
    7. ftp://ftp.gafol.net/pub/cpan/
    12
    United Kingdom
    1. http://www.mirrorservice.org/sites/ftp.funet.fi/pub/languages/perl/CPAN/
    2. ftp://ftp.mirrorservice.org/sites/ftp.funet.fi/pub/languages/perl/CPAN/
    3. http://mirror.tje.me.uk/pub/mirrors/ftp.cpan.org/
    4. ftp://mirror.tje.me.uk/pub/mirrors/ftp.cpan.org/
    5. http://www.mirror.8086.net/sites/CPAN/
    6. ftp://ftp.mirror.8086.net/sites/CPAN/
    7. http://cpan.mirror.anlx.net/
    8. ftp://ftp.mirror.anlx.net/CPAN/
    9. http://mirror.bytemark.co.uk/CPAN/
    10. ftp://mirror.bytemark.co.uk/CPAN/
    11. http://cpan.etla.org/
    12. ftp://cpan.etla.org/pub/CPAN
    13. ftp://ftp.demon.co.uk/pub/CPAN/
    14. http://mirror.sov.uk.goscomb.net/CPAN/
    15. ftp://mirror.sov.uk.goscomb.net/pub/CPAN/
    16. http://ftp.plig.net/pub/CPAN/
    17. ftp://ftp.plig.net/pub/CPAN/
    18. http://ftp.ticklers.org/pub/CPAN/
    19. ftp://ftp.ticklers.org/pub/CPAN/
    20. http://cpan.mirrors.uk2.net/
    21. ftp://mirrors.uk2.net/pub/CPAN/
    22. http://mirror.ox.ac.uk/sites/www.cpan.org/
    23. ftp://mirror.ox.ac.uk/sites/www.cpan.org/

North America

    12
    Bahamas
    1. http://www.securehost.com/mirror/CPAN/
    12
    Canada
    1. http://cpan.justanotherperlhacker.com/pub/CPAN/
    2. ftp://cpan.justanotherperlhacker.com/pub/CPAN/
    3. http://cpan.arcticnetwork.ca
    4. ftp://mirror.arcticnetwork.ca/pub/CPAN
    5. http://cpan.sunsite.ualberta.ca/
    6. ftp://cpan.sunsite.ualberta.ca/pub/CPAN/
    7. http://theoryx5.uwinnipeg.ca/pub/CPAN/
    8. ftp://theoryx5.uwinnipeg.ca/pub/CPAN/
    9. http://arwen.cs.dal.ca/mirror/CPAN/
    10. ftp://arwen.cs.dal.ca/pub/mirror/CPAN/
    11. http://CPAN.mirror.rafal.ca/
    12. ftp://CPAN.mirror.rafal.ca/pub/CPAN/
    13. ftp://ftp.nrc.ca/pub/CPAN/
    14. http://mirror.csclub.uwaterloo.ca/pub/CPAN/
    15. ftp://mirror.csclub.uwaterloo.ca/pub/CPAN/
    12
    Mexico
    1. http://www.msg.com.mx/CPAN/
    2. ftp://ftp.msg.com.mx/pub/CPAN/
    12
    United States
      12
      Alabama
      1. http://mirror.hiwaay.net/CPAN/
      2. ftp://mirror.hiwaay.net/CPAN/
      12
      California
      1. http://cpan.knowledgematters.net/
      2. http://cpan.binkerton.com/
      3. http://cpan.develooper.com/
      4. http://mirrors.gossamer-threads.com/CPAN
      5. http://cpan.schatt.com/
      6. http://mirrors.kernel.org/cpan/
      7. ftp://mirrors.kernel.org/pub/CPAN
      8. http://mirrors2.kernel.org/cpan/
      9. ftp://mirrors2.kernel.org/pub/CPAN/
      10. http://cpan.mirrors.redwire.net/
      11. http://cpan.mirror.facebook.net/
      12. http://mirrors1.kernel.org/cpan/
      13. ftp://mirrors1.kernel.org/pub/CPAN/
      14. http://cpan-sj.viaverio.com/
      15. ftp://cpan-sj.viaverio.com/pub/CPAN/
      16. http://www.perl.com/CPAN/
      17. http://cpan.yahoo.com/
      12
      Florida
      1. ftp://ftp.cise.ufl.edu/pub/mirrors/CPAN/
      2. http://mirror.atlantic.net/pub/CPAN/
      3. ftp://mirror.atlantic.net/pub/CPAN/
      4. http://mirror.candidhosting.com/pub/CPAN
      5. ftp://mirror.candidhosting.com/pub/CPAN
      12
      Idaho
      1. http://mirror.its.uidaho.edu/pub/cpan/
      2. ftp://mirror.its.uidaho.edu/cpan/
      12
      Illinois
      1. http://cpan.mirrors.hoobly.com/
      2. http://cpan.uchicago.edu/pub/CPAN/
      3. ftp://cpan.uchicago.edu/pub/CPAN/
      4. http://mirrors.servercentral.net/CPAN/
      5. http://www.stathy.com/CPAN/
      6. ftp://www.stathy.com/CPAN/
      12
      Indiana
      1. ftp://ftp.uwsg.iu.edu/pub/perl/CPAN/
      2. http://cpan.netnitco.net/
      3. ftp://cpan.netnitco.net/pub/mirrors/CPAN/
      4. http://ftp.ndlug.nd.edu/pub/perl/
      5. ftp://ftp.ndlug.nd.edu/pub/perl/
      6. http://fx.saintjoe.edu/pub/CPAN
      12
      Massachusetts
      1. ftp://ftp.ccs.neu.edu/net/mirrors/ftp.funet.fi/pub/languages/perl/CPAN/
      12
      Michigan
      1. http://ftp.wayne.edu/cpan/
      2. ftp://ftp.wayne.edu/cpan/
      12
      Minnesota
      1. http://cpan.msi.umn.edu/
      12
      New Jersey
      1. http://mirror.datapipe.net/CPAN/
      2. ftp://mirror.datapipe.net/pub/CPAN/
      12
      New York
      1. http://mirrors.24-7-solutions.net/pub/CPAN/
      2. ftp://mirrors.24-7-solutions.net/pub/CPAN/
      3. http://mirror.cc.columbia.edu/pub/software/cpan/
      4. ftp://mirror.cc.columbia.edu/pub/software/cpan/
      5. http://cpan.belfry.net/
      6. http://cpan.erlbaum.net/
      7. ftp://cpan.erlbaum.net/CPAN/
      8. http://cpan.hexten.net/
      9. ftp://cpan.hexten.net/
      10. http://ftp.fxcorporate.com/CPAN/
      11. ftp://ftp.fxcorporate.com/pub/CPAN/
      12. ftp://mirror.nyi.net/CPAN/
      13. http://mirror.rit.edu/CPAN/
      14. ftp://mirror.rit.edu/CPAN/
      12
      North Carolina
      1. http://www.ibiblio.org/pub/mirrors/CPAN
      2. ftp://ftp.ncsu.edu/pub/mirror/CPAN/
      12
      Oregon
      1. http://ftp.osuosl.org/pub/CPAN/
      2. ftp://ftp.osuosl.org/pub/CPAN/
      12
      Pennsylvania
      1. http://ftp.epix.net/CPAN/
      2. ftp://ftp.epix.net/pub/languages/perl/
      3. http://cpan.pair.com/
      4. ftp://cpan.pair.com/pub/CPAN/
      12
      South Carolina
      1. http://cpan.mirror.clemson.edu/
      12
      Tennessee
      1. http://mira.sunsite.utk.edu/CPAN/
      12
      Texas
      1. http://mirror.uta.edu/CPAN
      12
      Utah
      1. http://cpan.cs.utah.edu
      2. ftp://cpan.cs.utah.edu/pub/CPAN/
      3. ftp://mirror.xmission.com/CPAN/
      12
      Virginia
      1. http://cpan-du.viaverio.com/
      2. ftp://cpan-du.viaverio.com/pub/CPAN/
      3. http://perl.secsup.org/
      4. ftp://perl.secsup.org/pub/perl/
      5. ftp://mirror.cogentco.com/pub/CPAN/
      12
      Washington
      1. http://cpan.llarian.net/
      2. ftp://cpan.llarian.net/pub/CPAN/
      3. ftp://ftp-mirror.internap.com/pub/CPAN/
      12
      Wisconsin
      1. http://cpan.mirrors.tds.net
      2. ftp://cpan.mirrors.tds.net/pub/CPAN
      3. http://mirror.sit.wisc.edu/pub/CPAN/
      4. ftp://mirror.sit.wisc.edu/pub/CPAN/

Oceania

    12
    Australia
    1. http://mirror.internode.on.net/pub/cpan/
    2. ftp://mirror.internode.on.net/pub/cpan/
    3. http://cpan.mirror.aussiehq.net.au/
    4. http://mirror.as24220.net/cpan/
    5. ftp://mirror.as24220.net/cpan/
    12
    New Zealand
    1. ftp://ftp.auckland.ac.nz/pub/perl/CPAN/
    2. http://cpan.inspire.net.nz
    3. ftp://cpan.inspire.net.nz/cpan
    4. http://cpan.catalyst.net.nz/CPAN/
    5. ftp://cpan.catalyst.net.nz/pub/CPAN/

South America

    12
    Argentina
    1. http://cpan.patan.com.ar/
    2. http://cpan.localhost.net.ar
    3. ftp://mirrors.localhost.net.ar/pub/mirrors/CPAN
    12
    Brazil
    1. ftp://cpan.pop-mg.com.br/pub/CPAN/
    2. http://ftp.pucpr.br/CPAN
    3. ftp://ftp.pucpr.br/CPAN
    4. http://cpan.kinghost.net/
    5. ftp://ftp.linorg.usp.br/CPAN
    12
    Chile
    1. http://cpan.dcc.uchile.cl/
    2. ftp://cpan.dcc.uchile.cl/pub/lang/cpan/
    12
    Colombia
    1. http://www.laqee.unal.edu.co/CPAN/

RSYNC Mirrors

  1. mirror.as24220.net::cpan
  2. cpan.inode.at::CPAN
  3. gd.tuwien.ac.at::CPAN
  4. ftp.belnet.be::packages/cpan
  5. rsync.linorg.usp.br::CPAN
  6. rsync.arcticnetwork.ca::CPAN
  7. CPAN.mirror.rafal.ca::CPAN
  8. mirror.csclub.uwaterloo.ca::CPAN
  9. theoryx5.uwinnipeg.ca::CPAN
  10. www.laqee.unal.edu.co::CPAN
  11. mirror.uni-c.dk::CPAN
  12. rsync.nic.funet.fi::CPAN
  13. rsync://distrib-coffee.ipsl.jussieu.fr/pub/mirrors/cpan/
  14. mir1.ovh.net::CPAN
  15. miroir-francais.fr::cpan
  16. ftp.crihan.fr::CPAN
  17. rsync://mirror.cict.fr/cpan/
  18. rsync://mirror.netcologne.de/cpan/
  19. ftp-stud.hs-esslingen.de::CPAN/
  20. ftp.gwdg.de::FTP/languages/perl/CPAN/
  21. cpan.mirror.iphh.net::CPAN
  22. cpan.cpantesters.org::cpan
  23. cpan.hu::CPAN
  24. komo.vlsm.org::CPAN
  25. mirror.unej.ac.id::cpan
  26. ftp.esat.net::/pub/languages/perl/CPAN
  27. ftp.heanet.ie::mirrors/ftp.perl.org/pub/CPAN
  28. rsync.panu.it::CPAN
  29. cpan.fastbull.org::CPAN
  30. ftp.kddilabs.jp::cpan
  31. ftp.nara.wide.ad.jp::cpan/
  32. rsync://ftp.jaist.ac.jp/pub/CPAN/
  33. rsync://ftp.riken.jp/cpan/
  34. mirror.linuxiso.kz::CPAN
  35. rsync://mirrors3.kernel.org/mirrors/CPAN/
  36. rsync://rsync.osmirror.nl/cpan/
  37. mirror.leaseweb.com::CPAN
  38. cpan.nautile.nc::CPAN
  39. mirror.icis.pcz.pl::CPAN
  40. piotrkosoft.net::mirrors/CPAN
  41. rsync://cpan.perl.pt/
  42. ftp.kaist.ac.kr::cpan
  43. cpan.sarang.net::CPAN
  44. mirror.averse.net::cpan
  45. rsync.oss.eznetsols.org
  46. mirror.ac.za::cpan
  47. ftp.is.co.za::IS-Mirror/ftp.cpan.org/
  48. rsync://ftp.gui.uva.es/cpan/
  49. rsync://mirrors4.kernel.org/mirrors/CPAN/
  50. ftp.solnet.ch::CPAN
  51. ftp.ulak.net.tr::CPAN
  52. gafol.net::cpan
  53. rsync.mirrorservice.org::ftp.funet.fi/pub/
  54. rsync://rsync.mirror.8086.net/CPAN/
  55. rsync.mirror.anlx.net::CPAN
  56. mirror.bytemark.co.uk::CPAN
  57. ftp.plig.net::CPAN
  58. rsync://ftp.ticklers.org:CPAN/
  59. mirrors.ibiblio.org::CPAN
  60. cpan-du.viaverio.com::CPAN
  61. mirror.hiwaay.net::CPAN
  62. rsync://mira.sunsite.utk.edu/CPAN/
  63. cpan.mirrors.tds.net::CPAN
  64. mirror.its.uidaho.edu::cpan
  65. rsync://mirror.cc.columbia.edu::cpan/
  66. ftp.fxcorporate.com::CPAN
  67. rsync.atlantic.net::CPAN
  68. mirrors.kernel.org::mirrors/CPAN
  69. rsync://mirrors2.kernel.org/mirrors/CPAN/
  70. cpan.pair.com::CPAN
  71. rsync://mirror.rit.edu/CPAN/
  72. rsync://mirror.facebook.net/cpan/
  73. rsync://mirrors1.kernel.org/mirrors/CPAN/
  74. cpan-sj.viaverio.com::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.,:

    1. sub new {
    2. my $class = shift;
    3. return bless {}, $class;
    4. }

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

    1. sub new {
    2. my $self = shift;
    3. my $class = ref($self) || $self;
    4. return bless {}, $class;
    5. }

    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:

    1. 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 = YOURCLASS->new(); into: $obj = SUBCLASS->new(); ?

    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 perlstyle.

    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:

    1. $ALL_CAPS_HERE constants only (beware clashes with Perl vars)
    2. $Some_Caps_Here package-wide global/static
    3. $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:

      1. Copyright (c) 1995 Your Name. All rights reserved.
      2. This program is free software; you can redistribute it and/or
      3. 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:

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

      or upload to one of these sites:

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

      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:

    1. % perl -e 'use Module::Name; method(@ARGV)' ...
    2. or
    3. % 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.