PERLMODLIB(1)

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

autodie
    Replace functions with ones that succeed or die with lexical scope

autodie::exception
    Exceptions from autodying functions.

autodie::exception::system
    Exceptions from autodying system().

autodie::hints
    Provide hints about user subroutines to autodie

autodie::skip
    Skip a package when throwing autodie exceptions

autouse
    Postpone load of modules until a function is used

base
    Establish an ISA relationship with base classes at compile time

bigfloat
    Transparent big floating point number support for Perl

bigint
    Transparent big integer support for Perl

bignum
    Transparent big number support for Perl

bigrat
    Transparent big rational number support for Perl

blib
    Use MakeMaker's uninstalled version of a package

builtin
    Import built-in utility functions

bytes
    Expose the individual bytes of characters

charnames
    Access to Unicode character names and named character sequences; also define character names

constant
    Declare constants

deprecate
    Perl pragma for deprecating the inclusion of a module in core

diagnostics
    Produce verbose warning diagnostics

encoding
    Allows you to write your script in non-ASCII and non-UTF-8

encoding::warnings
    Warn on implicit encoding conversions

experimental
    Experimental features made easy

feature
    Enable new features

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

lib Manipulate @INC at compile time

locale
    Use or avoid POSIX locales for built-in operations

mro Method Resolution Order

ok  Alternative to Test::More::use_ok

open
    Set default PerlIO layers for input and output

ops Restrict unsafe operations when compiling

overload
    Package for overloading Perl operations

overloading
    Lexically control overloading

parent
    Establish an ISA relationship with base classes at compile time

re  Alter regular expression behaviour

sigtrap
    Enable simple signal handling

sort
    Control sort() behaviour

source::encoding
    Declare Perl source code encoding

stable
    Experimental features made easy, once we know they're stable

strict
    Restrict unsafe constructs

subs
    Predeclare subroutine names

threads
    Perl interpreter-based threads

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

version
    Perl extension for Version Objects

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.

Amiga::ARexx
    Perl extension for ARexx support

Amiga::Exec
    Perl extension for low level amiga support

AnyDBM_File
    Provide framework for multiple DBMs

App::Cpan
    Easily interact with CPAN from the command line

App::Prove
    Implements the "prove" command.

App::Prove::State
    State storage for the "prove" command.

App::Prove::State::Result
    Individual test suite results.

App::Prove::State::Result::Test
    Individual test results.

Archive::Tar
    Module for manipulations of tar archives

Archive::Tar::File
    A subclass for in-memory extracted file from Archive::Tar

Attribute::Handlers
    Simpler definition of attribute handlers

AutoLoader
    Load subroutines only on demand

AutoSplit
    Split a package for autoloading

B   The Perl Compiler Backend

B::Concise
    Walk Perl syntax tree, printing concise info about ops

B::Deparse
    Perl compiler backend to produce perl code

B::Op_private
    OP op_private flag definitions

B::Showlex
    Show lexical variables used in functions or files

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

"IO::Socket::IP"
    Family-neutral IP socket supporting both IPv4 and IPv6

"Socket"
    Networking constants and support functions

"Test2::Tools::Refcount"
    Assert reference counts on objects

CORE
    Namespace for Perl's core routines

CPAN
    Query, download and build perl modules from CPAN sites

CPAN::API::HOWTO
    A recipe book for programming with CPAN.pm

CPAN::Debug
    Internal debugging for CPAN.pm

CPAN::Distroprefs
    Read and match distroprefs

CPAN::FirstTime
    Utility for CPAN::Config file Initialization

CPAN::HandleConfig
    Internal configuration handling for CPAN.pm

CPAN::Kwalify
    Interface between CPAN.pm and Kwalify.pm

CPAN::Meta
    The distribution metadata for a CPAN dist

CPAN::Meta::Converter
    Convert CPAN distribution metadata structures

CPAN::Meta::Feature
    An optional feature provided by a CPAN distribution

CPAN::Meta::History
    History of CPAN Meta Spec changes

CPAN::Meta::History::Meta_1_0
    Version 1.0 metadata specification for META.yml

CPAN::Meta::History::Meta_1_1
    Version 1.1 metadata specification for META.yml

CPAN::Meta::History::Meta_1_2
    Version 1.2 metadata specification for META.yml

CPAN::Meta::History::Meta_1_3
    Version 1.3 metadata specification for META.yml

CPAN::Meta::History::Meta_1_4
    Version 1.4 metadata specification for META.yml

CPAN::Meta::Merge
    Merging CPAN Meta fragments

CPAN::Meta::Prereqs
    A set of distribution prerequisites by phase and type

CPAN::Meta::Requirements
    A set of version requirements for a CPAN dist

CPAN::Meta::Requirements::Range
    A set of version requirements for a CPAN dist

CPAN::Meta::Spec
    Specification for CPAN distribution metadata

CPAN::Meta::Validator
    Validate CPAN distribution metadata structures

CPAN::Meta::YAML
    Read and write a subset of YAML for CPAN Meta files

CPAN::Nox
    Wrapper around CPAN.pm without using any XS module

CPAN::Plugin
    Base class for CPAN shell extensions

CPAN::Plugin::Specfile
    Proof of concept implementation of a trivial CPAN::Plugin

CPAN::Queue
    Internal queue support for CPAN.pm

CPAN::Tarzip
    Internal handling of tar archives for CPAN.pm

CPAN::Version
    Utility functions to compare CPAN versions

Carp
    Alternative warn and die for modules

Class::Struct
    Declare struct-like datatypes as Perl classes

Compress::Raw::Bzip2
    Low-Level Interface to bzip2 compression library

Compress::Raw::Zlib
    Low-Level Interface to zlib or zlib-ng compression library

Compress::Zlib
    Interface to zlib compression library

Config
    Access Perl configuration information

Config::Extensions
    Hash lookup of which core extensions were built.

Config::Perl::V
    Structured data retrieval of perl -V output

Configure
    Provide auto-configuration utilities

Cwd Get pathname of current working directory

DB  Programmatic interface to the Perl debugging API

DBM_Filter
    Filter DBM keys/values

DBM_Filter::compress
    Filter for DBM_Filter

DBM_Filter::encode
    Filter for DBM_Filter

DBM_Filter::int32
    Filter for DBM_Filter

DBM_Filter::null
    Filter for DBM_Filter

DBM_Filter::utf8
    Filter for DBM_Filter

DB_File
    Perl5 access to Berkeley DB version 1.x

Data::Dumper
    Stringified perl data structures, suitable for both printing and "eval"

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::SHA
    Perl extension for SHA-1/224/256/384/512

Digest::base
    Digest base class

Digest::file
    Calculate digests of files

DirHandle
    (obsolete) supply object methods for directory handles

Dumpvalue
    Provides screen dump of Perl data.

DynaLoader
    Dynamically load C libraries into Perl code

Encode
    Character encodings in Perl

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::GSM0338
    ETSI GSM 03.38 Encoding

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 encoding for an unstructured email header

Encode::MIME::Name
    Internally used by Encode

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::CBuilder
    Compile and link C code for Perl modules

ExtUtils::CBuilder::Platform::Windows
    Builder class for Windows platforms

ExtUtils::Command
    Utilities to replace common UNIX commands in Makefiles etc.

ExtUtils::Command::MM
    Commands for the MM's to use in Makefiles

ExtUtils::Constant
    Generate XS code to import C header constants

ExtUtils::Constant::Base
    Base class for ExtUtils::Constant objects

ExtUtils::Constant::Utils
    Helper functions for ExtUtils::Constant

ExtUtils::Constant::XS
    Generate C code for XS modules' 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_AIX
    AIX specific subclass of ExtUtils::MM_Unix

ExtUtils::MM_Any
    Platform-agnostic MM methods

ExtUtils::MM_BeOS
    Methods to override UN*X behaviour in ExtUtils::MakeMaker

ExtUtils::MM_Cygwin
    Methods to override UN*X behaviour in ExtUtils::MakeMaker

ExtUtils::MM_DOS
    DOS specific subclass of ExtUtils::MM_Unix

ExtUtils::MM_Darwin
    Special behaviors for OS X

ExtUtils::MM_MacOS
    Once produced Makefiles for MacOS Classic

ExtUtils::MM_NW5
    Methods to override UN*X behaviour in ExtUtils::MakeMaker

ExtUtils::MM_OS2
    Methods to override UN*X behaviour in ExtUtils::MakeMaker

ExtUtils::MM_OS390
    OS390 specific subclass of ExtUtils::MM_Unix

ExtUtils::MM_QNX
    QNX specific subclass of ExtUtils::MM_Unix

ExtUtils::MM_UWIN
    U/WIN specific subclass of ExtUtils::MM_Unix

ExtUtils::MM_Unix
    Methods used by ExtUtils::MakeMaker

ExtUtils::MM_VMS
    Methods to override UN*X behaviour in ExtUtils::MakeMaker

ExtUtils::MM_VOS
    VOS specific subclass of ExtUtils::MM_Unix

ExtUtils::MM_Win32
    Methods to override UN*X behaviour in ExtUtils::MakeMaker

ExtUtils::MM_Win95
    Method to customize MakeMaker for Win9X

ExtUtils::MY
    ExtUtils::MakeMaker subclass for customization

ExtUtils::MakeMaker
    Create a module Makefile

ExtUtils::MakeMaker::Config
    Wrapper around Config.pm

ExtUtils::MakeMaker::FAQ
    Frequently Asked Questions About MakeMaker

ExtUtils::MakeMaker::Locale
    Bundled Encode::Locale

ExtUtils::MakeMaker::Tutorial
    Writing a module with MakeMaker

ExtUtils::Manifest
    Utilities to write and check a MANIFEST file

ExtUtils::Miniperl
    Write the C code for miniperlmain.c and perlmain.c

ExtUtils::Mkbootstrap
    Make a bootstrap file for use by DynaLoader

ExtUtils::Mksymlists
    Write linker options files for dynamic extension

ExtUtils::PL2Bat
    Batch file creation to run perl scripts on Windows

ExtUtils::Packlist
    Manage .packlist files

ExtUtils::ParseXS
    Converts Perl XS code into C code

ExtUtils::ParseXS::Constants
    Initialization values for some globals

ExtUtils::ParseXS::Eval
    Clean package to evaluate code in

ExtUtils::ParseXS::Node
    Classes for nodes of an ExtUtils::ParseXS AST

ExtUtils::ParseXS::Utilities
    Subroutines used with ExtUtils::ParseXS

ExtUtils::Typemaps
    Read/Write/Modify Perl/XS typemap files

ExtUtils::Typemaps::Cmd
    Quick commands for handling typemaps

ExtUtils::Typemaps::InputMap
    Entry in the INPUT section of a typemap

ExtUtils::Typemaps::OutputMap
    Entry in the OUTPUT section of a typemap

ExtUtils::Typemaps::Type
    Entry in the TYPEMAP section of a typemap

ExtUtils::XSSymSet
    Keep sets of symbol names palatable to the VMS linker

ExtUtils::testlib
    Add blib/* directories to @INC

Fatal
    Replace functions with equivalents which succeed or die

Fcntl
    Various flag constants and helper functions from C's fcntl.h

File::Basename
    Parse file paths into directory, filename and suffix.

File::Compare
    Compare files or filehandles

File::Copy
    Copy files or filehandles

File::DosGlob
    DOS like globbing and then some

File::Fetch
    A generic file fetching mechanism

File::Find
    Traverse a directory tree.

File::Glob
    Perl extension for BSD glob routine

File::GlobMapper
    Extend File Glob to Allow Input and Output Files

File::Path
    Create or remove directory trees

File::Spec
    Portably perform operations on file names

File::Spec::AmigaOS
    File::Spec for AmigaOS

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::Long::Parser
    Getopt::Long object-oriented interface

Getopt::Std
    Process single-character switches with switch clustering

HTTP::Tiny
    A small, simple, correct HTTP/1.1 client

Hash::Util
    A selection of general-utility hash subroutines

Hash::Util::FieldHash
    Support for Inside-Out Classes

I18N::Collate
    Compare 8-bit scalar data according to the current locale

I18N::LangTags
    Functions for dealing with RFC3066-style language tags

I18N::LangTags::Detect
    Detect the user's language preferences

I18N::LangTags::List
    Tags and names for human languages

I18N::Langinfo
    Query locale information

IO  Load various IO modules

IO::Compress
    Read/write compressed data in multiple formats

IO::Compress::Base
    Base Class for IO::Compress modules

IO::Compress::Bzip2
    Write bzip2 files/buffers

IO::Compress::Deflate
    Write RFC 1950 files/buffers

IO::Compress::FAQ
    Frequently Asked Questions about IO::Compress

IO::Compress::Gzip
    Write RFC 1952 files/buffers

IO::Compress::RawDeflate
    Write RFC 1951 files/buffers

IO::Compress::Zip
    Write zip files/buffers

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

IO::Uncompress::AnyInflate
    Uncompress zlib-based (zip, gzip) file/buffer

IO::Uncompress::AnyUncompress
    Uncompress gzip, zip, bzip2, zstd, xz, lzma, lzip, lzf or lzop file/buffer

IO::Uncompress::Base
    Base Class for IO::Uncompress modules

IO::Uncompress::Bunzip2
    Read bzip2 files/buffers

IO::Uncompress::Gunzip
    Read RFC 1952 files/buffers

IO::Uncompress::Inflate
    Read RFC 1950 files/buffers

IO::Uncompress::RawInflate
    Read RFC 1951 files/buffers

IO::Uncompress::Unzip
    Read zip files/buffers

IO::Zlib
    IO:: style interface to Compress::Zlib

IPC::Cmd
    Finding and running system commands made easy

IPC::Msg
    SysV Msg IPC object class

IPC::Open2
    Open a process for both reading and writing using open2()

IPC::Open3
    Open a process for reading, writing, and error handling using open3()

IPC::Semaphore
    SysV Semaphore IPC object class

IPC::SharedMem
    SysV Shared Memory IPC object class

IPC::SysV
    System V IPC constants and system calls

Internals
    Reserved special namespace for internals related functions

JSON::PP
    JSON::XS compatible pure-Perl module.

JSON::PP::Boolean
    Dummy module providing JSON::PP::Boolean

List::Util
    A selection of general-utility list subroutines

List::Util::XS
    Indicate if List::Util was compiled with a C compiler

Locale::Maketext
    Framework for localization

Locale::Maketext::Cookbook
    Recipes for using Locale::Maketext

Locale::Maketext::Guts
    Deprecated module to load Locale::Maketext utf8 code

Locale::Maketext::GutsLoader
    Deprecated module to load Locale::Maketext utf8 code

Locale::Maketext::Simple
    Simple interface to Locale::Maketext::Lexicon

Locale::Maketext::TPJ13
    Article about software localization

MIME::Base64
    Encoding and decoding of base64 strings

MIME::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::BigInt::FastCalc
    Math::BigInt::Calc with some XS for more speed

Math::BigInt::Lib
    Virtual parent class for Math::BigInt libraries

Math::BigRat
    Arbitrary size rational number math package

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::NDBM_File
    Glue to provide EXISTS for NDBM_File for Storable use

Memoize::SDBM_File
    DEPRECATED compatibility shim

Memoize::Storable
    Store Memoized data in Storable database

Module::CoreList
    What modules shipped with versions of perl

Module::CoreList::Utils
    What utilities shipped with versions of perl

Module::Load
    Runtime require of both modules and files

Module::Load::Conditional
    Looking up module information / loading at runtime

Module::Loaded
    Mark modules as loaded or unloaded

Module::Metadata
    Gather package and POD information from perl module files

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::FTP::dataconn
    FTP Client data connection 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

OpenBSD::Pledge
    Perl interface to OpenBSD pledge(2)

OpenBSD::Unveil
    Perl interface to OpenBSD unveil(2)

POSIX
    Perl interface to IEEE Std 1003.1

Params::Check
    A generic input parsing/checking mechanism.

Parse::CPAN::Meta
    Parse META.yml and META.json CPAN metadata files

Perl::OSType
    Map Perl operating system names to generic types

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

PerlIO::encoding
    Encoding layer

PerlIO::mmap
    Memory mapped IO

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::Escapes
    For resolving Pod E<...> sequences

Pod::Functions
    Group Perl's functions a la perlfunc.pod

Pod::Html
    Module to convert pod files to HTML

Pod::Html::Util
    Helper functions for Pod-Html

Pod::Man
    Convert POD data to formatted *roff input

Pod::ParseLink
    Parse an L<> formatting code in POD text

Pod::Perldoc
    Look up Perl documentation in Pod format.

Pod::Perldoc::BaseTo
    Base for Pod::Perldoc formatters

Pod::Perldoc::GetOptsOO
    Customized option parser for Pod::Perldoc

Pod::Perldoc::ToANSI
    Render Pod with ANSI color escapes

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::ToTerm
    Render Pod with terminal escapes

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::Simple
    Framework for parsing Pod

Pod::Simple::Checker
    Check the Pod syntax of a document

Pod::Simple::Debug
    Put Pod::Simple into trace/debug mode

Pod::Simple::DumpAsText
    Dump Pod-parsing events as text

Pod::Simple::DumpAsXML
    Turn Pod into XML

Pod::Simple::HTML
    Convert Pod to HTML

Pod::Simple::HTMLBatch
    Convert several Pod files to several HTML files

Pod::Simple::JustPod
    Just the Pod, the whole Pod, and nothing but the Pod

Pod::Simple::LinkSection
    Represent "section" attributes of L codes

Pod::Simple::Methody
    Turn Pod::Simple events into method calls

Pod::Simple::PullParser
    A pull-parser interface to parsing Pod

Pod::Simple::PullParserEndToken
    End-tokens from Pod::Simple::PullParser

Pod::Simple::PullParserStartToken
    Start-tokens from Pod::Simple::PullParser

Pod::Simple::PullParserTextToken
    Text-tokens from Pod::Simple::PullParser

Pod::Simple::PullParserToken
    Tokens from Pod::Simple::PullParser

Pod::Simple::RTF
    Format Pod as RTF

Pod::Simple::Search
    Find POD documents in directory trees

Pod::Simple::SimpleTree
    Parse Pod into a simple parse tree

Pod::Simple::Subclassing
    Write a formatter as a Pod::Simple subclass

Pod::Simple::Text
    Format Pod as plaintext

Pod::Simple::TextContent
    Get the text content of Pod

Pod::Simple::XHTML
    Format Pod as validating XHTML

Pod::Simple::XMLOutStream
    Turn Pod into XML

Pod::Text
    Convert POD data to formatted 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
    Extracts POD documentation and shows usage information

SDBM_File
    Tied access to sdbm files

Safe
    Compile and execute code in restricted compartments

Scalar::List::Utils
    A distribution of general-utility subroutines

Scalar::Util
    A selection of general-utility scalar subroutines

Search::Dict
    Look - search for key in dictionary file

SelectSaver
    Save and restore selected file handle

SelfLoader
    Load functions only on demand

Storable
    Persistence for Perl data structures

Sub::Util
    A selection of utility subroutines for subs and CODE references

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

Sys::Syslog::Win32
    Win32 support for Sys::Syslog

TAP::Base
    Base class that provides common functionality to TAP::Parser

TAP::Formatter::Base
    Base class for harness output delegates

TAP::Formatter::Color
    Run Perl test scripts with color

TAP::Formatter::Console
    Harness output delegate for default console output

TAP::Formatter::Console::ParallelSession
    Harness output delegate for parallel console output

TAP::Formatter::Console::Session
    Harness output delegate for default console output

TAP::Formatter::File
    Harness output delegate for file output

TAP::Formatter::File::Session
    Harness output delegate for file output

TAP::Formatter::Session
    Abstract base class for harness output delegate

TAP::Harness
    Run test scripts with statistics

TAP::Harness::Env
    Parsing harness related environmental variables where appropriate

TAP::Object
    Base class that provides common functionality to all "TAP::*" modules

TAP::Parser
    Parse TAP output

TAP::Parser::Aggregator
    Aggregate TAP::Parser results

TAP::Parser::Grammar
    A grammar for the Test Anything Protocol.

TAP::Parser::Iterator
    Base class for TAP source iterators

TAP::Parser::Iterator::Array
    Iterator for array-based TAP sources

TAP::Parser::Iterator::Process
    Iterator for process-based TAP sources

TAP::Parser::Iterator::Stream
    Iterator for filehandle-based TAP sources

TAP::Parser::IteratorFactory
    Figures out which SourceHandler objects to use for a given Source

TAP::Parser::Multiplexer
    Multiplex multiple TAP::Parsers

TAP::Parser::Result
    Base class for TAP::Parser output objects

TAP::Parser::Result::Bailout
    Bailout result token.

TAP::Parser::Result::Comment
    Comment result token.

TAP::Parser::Result::Plan
    Plan result token.

TAP::Parser::Result::Pragma
    TAP pragma token.

TAP::Parser::Result::Test
    Test result token.

TAP::Parser::Result::Unknown
    Unknown result token.

TAP::Parser::Result::Version
    TAP syntax version token.

TAP::Parser::Result::YAML
    YAML result token.

TAP::Parser::ResultFactory
    Factory for creating TAP::Parser output objects

TAP::Parser::Scheduler
    Schedule tests during parallel testing

TAP::Parser::Scheduler::Job
    A single testing job.

TAP::Parser::Scheduler::Spinner
    A no-op job.

TAP::Parser::Source
    A TAP source & meta data about it

TAP::Parser::SourceHandler
    Base class for different TAP source handlers

TAP::Parser::SourceHandler::Executable
    Stream output from an executable TAP source

TAP::Parser::SourceHandler::File
    Stream TAP from a text file.

TAP::Parser::SourceHandler::Handle
    Stream TAP from an IO::Handle or a GLOB.

TAP::Parser::SourceHandler::Perl
    Stream TAP from a Perl executable

TAP::Parser::SourceHandler::RawTAP
    Stream output from raw TAP in a scalar/array ref.

TAP::Parser::YAMLish::Reader
    Read YAMLish data from iterator

TAP::Parser::YAMLish::Writer
    Write YAMLish data

Term::ANSIColor
    Color screen output using ANSI escape sequences

Term::Cap
    Perl termcap interface

Term::Complete
    Perl word completion module

Term::ReadKey
    A perl module for simple terminal control

Term::ReadLine
    Perl interface to various "readline" packages.

Term::Table
    Format a header and rows into a table

Term::Table::Cell
    Representation of a cell in a table.

Term::Table::CellStack
    Combine several cells into one (vertical)

Term::Table::HashBase
    Build hash based classes.

Term::Table::LineBreak
    Break up lines for use in tables.

Term::Table::Util
    Utilities for Term::Table.

Test
    Provides a simple framework for writing test scripts

Test2
    Framework for writing test tools that all work together.

Test2::API
    Primary interface for writing Test2 based testing tools.

Test2::API::Breakage
    What breaks at what version

Test2::API::Context
    Object to represent a testing context.

Test2::API::Instance
    Object used by Test2::API under the hood

Test2::API::InterceptResult
    Representation of a list of events.

Test2::API::InterceptResult::Event
    Representation of an event for use in

Test2::API::InterceptResult::Hub
    Hub used by InterceptResult.

Test2::API::InterceptResult::Squasher
    Encapsulation of the algorithm that

Test2::API::Stack
    Object to manage a stack of Test2::Hub

Test2::AsyncSubtest
    Object representing an async subtest.

Test2::AsyncSubtest::Event::Attach
    Event to attach a subtest to the parent.

Test2::AsyncSubtest::Event::Detach
    Event to detach a subtest from the parent.

Test2::AsyncSubtest::Hub
    Hub used by async subtests.

Test2::Bundle
    Documentation for bundles.

Test2::Bundle::Extended
    Old name for Test2::V0

Test2::Bundle::More
    ALMOST a drop-in replacement for Test::More.

Test2::Bundle::Simple
    ALMOST a drop-in replacement for Test::Simple.

Test2::Compare
    Test2 extension for writing deep comparison tools.

Test2::Compare::Array
    Internal representation of an array comparison.

Test2::Compare::Bag
    Internal representation of a bag comparison.

Test2::Compare::Base
    Base class for comparison classes.

Test2::Compare::Bool
    Compare two values as booleans

Test2::Compare::Custom
    Custom field check for comparisons.

Test2::Compare::DeepRef
    Ref comparison

Test2::Compare::Delta
    Representation of differences between nested data

Test2::Compare::Event
    Event specific Object subclass.

Test2::Compare::EventMeta
    Meta class for events in deep comparisons

Test2::Compare::Float
    Compare two values as numbers with tolerance.

Test2::Compare::Hash
    Representation of a hash in a deep comparison.

Test2::Compare::Isa
    Check if the value is an instance of the class.

Test2::Compare::Meta
    Check library for meta-checks

Test2::Compare::Negatable
    Poor mans 'role' for compare objects that can be negated.

Test2::Compare::Number
    Compare two values as numbers

Test2::Compare::Object
    Representation of an object during deep

Test2::Compare::OrderedSubset
    Internal representation of an ordered subset.

Test2::Compare::Pattern
    Use a pattern to validate values in a deep

Test2::Compare::Ref
    Ref comparison

Test2::Compare::Regex
    Regex direct comparison

Test2::Compare::Scalar
    Representation of a Scalar Ref in deep

Test2::Compare::Set
    Allows a field to be matched against a set of

Test2::Compare::String
    Compare two values as strings

Test2::Compare::Undef
    Check that something is undefined

Test2::Compare::Wildcard
    Placeholder check.

Test2::Env
    Documentation for environment variables used or set by Test2.

Test2::Event
    Base class for events

Test2::Event::Bail
    Bailout!

Test2::Event::Diag
    Diag event type

Test2::Event::Encoding
    Set the encoding for the output stream

Test2::Event::Exception
    Exception event

Test2::Event::Fail
    Event for a simple failed assertion

Test2::Event::Generic
    Generic event type.

Test2::Event::Note
    Note event type

Test2::Event::Ok
    Ok event type

Test2::Event::Pass
    Event for a simple passing assertion

Test2::Event::Plan
    The event of a plan

Test2::Event::Skip
    Skip event type

Test2::Event::Subtest
    Event for subtest types

Test2::Event::TAP::Version
    Event for TAP version.

Test2::Event::V2
    Second generation event.

Test2::Event::Waiting
    Tell all procs/threads it is time to be done

Test2::EventFacet
    Base class for all event facets.

Test2::EventFacet::About
    Facet with event details.

Test2::EventFacet::Amnesty
    Facet for assertion amnesty.

Test2::EventFacet::Assert
    Facet representing an assertion.

Test2::EventFacet::Control
    Facet for hub actions and behaviors.

Test2::EventFacet::Error
    Facet for errors that need to be shown.

Test2::EventFacet::Hub
    Facet for the hubs an event passes through.

Test2::EventFacet::Info
    Facet for information a developer might care about.

Test2::EventFacet::Info::Table
    Intermediary representation of a table.

Test2::EventFacet::Meta
    Facet for meta-data

Test2::EventFacet::Parent
    Facet for events contains other events

Test2::EventFacet::Plan
    Facet for setting the plan

Test2::EventFacet::Render
    Facet that dictates how to render an event.

Test2::EventFacet::Trace
    Debug information for events

Test2::Formatter
    Namespace for formatters.

Test2::Formatter::TAP
    Standard TAP formatter

Test2::Hub
    The conduit through which all events flow.

Test2::Hub::Interceptor
    Hub used by interceptor to grab results.

Test2::Hub::Interceptor::Terminator
    Exception class used by

Test2::Hub::Subtest
    Hub used by subtests

Test2::IPC
    Turn on IPC for threading or forking support.

Test2::IPC::Driver
    Base class for Test2 IPC drivers.

Test2::IPC::Driver::Files
    Temp dir + Files concurrency model.

Test2::Manual
    Documentation hub for Test2 and Test2-Suite.

Test2::Manual::Anatomy
    The hub for documentation of the inner workings of

Test2::Manual::Anatomy::API
    Internals documentation for the API.

Test2::Manual::Anatomy::Context
    Internals documentation for the Context

Test2::Manual::Anatomy::EndToEnd
    Overview of Test2 from load to finish.

Test2::Manual::Anatomy::Event
    The internals of events

Test2::Manual::Anatomy::Hubs
    Internals documentation for the hub stack, and

Test2::Manual::Anatomy::IPC
    Manual for the IPC system.

Test2::Manual::Anatomy::Utilities
    Overview of utilities for Test2.

Test2::Manual::Concurrency
    Documentation for Concurrency support.

Test2::Manual::Contributing
    How to contribute to the Test2 project.

Test2::Manual::Testing
    Hub for documentation about writing tests with Test2.

Test2::Manual::Testing::Introduction
    Introduction to testing with Test2.

Test2::Manual::Testing::Migrating
    How to migrate existing tests from

Test2::Manual::Testing::Planning
    The many ways to set a plan.

Test2::Manual::Testing::Todo
    Tutorial for marking tests as TODO.

Test2::Manual::Tooling
    Manual page for tool authors.

Test2::Manual::Tooling::FirstTool
    Write your first tool with Test2.

Test2::Manual::Tooling::Formatter
    How to write a custom formatter, in our

Test2::Manual::Tooling::Nesting
    Tutorial for using other tools within your

Test2::Manual::Tooling::Plugin::TestExit
    How to safely add pre-exit

Test2::Manual::Tooling::Plugin::TestingDone
    Run code when the test file is

Test2::Manual::Tooling::Plugin::ToolCompletes
    How to add behaviors that occur

Test2::Manual::Tooling::Plugin::ToolStarts
    How to add behaviors that occur

Test2::Manual::Tooling::Subtest
    How to implement a tool that makes use of

Test2::Manual::Tooling::TestBuilder
    This section maps Test::Builder methods

Test2::Manual::Tooling::Testing
    Tutorial on how to test your testing tools.

Test2::Mock
    Module for managing mocked classes and instances.

Test2::Plugin
    Documentation for plugins

Test2::Plugin::BailOnFail
    Automatically bail out of testing on the first test

Test2::Plugin::DieOnFail
    Automatically die on the first test failure.

Test2::Plugin::ExitSummary
    Add extra diagnostics on failure at the end of the

Test2::Plugin::SRand
    Control the random seed for more controlled test

Test2::Plugin::Times
    Output timing data at the end of the test.

Test2::Plugin::UTF8
    Test2 plugin to test with utf8.

Test2::Require
    Base class and documentation for skip-unless type test

Test2::Require::AuthorTesting
    Only run a test when the AUTHOR_TESTING

Test2::Require::AutomatedTesting
    Only run a test when the AUTOMATED_TESTING

Test2::Require::EnvVar
    Only run a test when a specific environment variable

Test2::Require::ExtendedTesting
    Only run a test when the EXTENDED_TESTING

Test2::Require::Fork
    Skip a test file unless the system supports forking

Test2::Require::Module
    Skip tests if certain packages are not installed, or

Test2::Require::NonInteractiveTesting
    Only run a test when the NONINTERACTIVE_TESTING

Test2::Require::Perl
    Skip the test unless the necessary version of Perl is

Test2::Require::RealFork
    Skip a test file unless the system supports true

Test2::Require::ReleaseTesting
    Only run a test when the RELEASE_TESTING

Test2::Require::Threads
    Skip a test file unless the system supports threading

Test2::Suite
    Distribution with a rich set of tools built upon the Test2

Test2::Todo
    TODO extension for Test2.

Test2::Tools
    Documentation for Tools.

Test2::Tools::AsyncSubtest
    Tools for writing async subtests.

Test2::Tools::Basic
    Test2 implementation of the basic testing tools.

Test2::Tools::Class
    Test2 implementation of the tools for testing classes.

Test2::Tools::ClassicCompare
    Classic (Test::More style) comparison tools.

Test2::Tools::Compare
    Tools for comparing deep data structures.

Test2::Tools::Defer
    Write tests that get executed at a later time

Test2::Tools::Encoding
    Tools for managing the encoding of Test2 based

Test2::Tools::Event
    Tools for generating test events.

Test2::Tools::Exception
    Test2 based tools for checking exceptions

Test2::Tools::Exports
    Tools for validating exporters.

Test2::Tools::GenTemp
    Tool for generating a populated temp directory.

Test2::Tools::Grab
    Temporarily intercept all events without adding a scope

Test2::Tools::Mock
    Class/Instance mocking for Test2.

Test2::Tools::Ref
    Tools for validating references.

Test2::Tools::Spec
    RSPEC implementation on top of Test2::Workflow

Test2::Tools::Subtest
    Tools for writing subtests

Test2::Tools::Target
    Alias the testing target package.

Test2::Tools::Tester
    Tools to help you test other testing tools.

Test2::Tools::Tiny
    Tiny set of tools for unfortunate souls who cannot use

Test2::Tools::Warnings
    Tools to verify warnings.

Test2::Transition
    Transition notes when upgrading to Test2

Test2::Util
    Tools used by Test2 and friends.

Test2::Util::ExternalMeta
    Allow third party tools to safely attach meta-data

Test2::Util::Facets2Legacy
    Convert facet data to the legacy event API.

Test2::Util::Grabber
    Object used to temporarily intercept all events.

Test2::Util::Guard
    Inline copy of Scope::Guard

Test2::Util::HashBase
    Build hash based classes.

Test2::Util::Importer
    Inline copy of Importer.

Test2::Util::Ref
    Tools for inspecting or manipulating references.

Test2::Util::Sig
    Signal tools used by Test2 and friends.

Test2::Util::Stash
    Utilities for manipulating stashes and globs.

Test2::Util::Sub
    Tools for inspecting and manipulating subs.

Test2::Util::Table
    Format a header and rows into a table

Test2::Util::Table::LineBreak
    Break up lines for use in tables.

Test2::Util::Times
    Format timing/benchmark information.

Test2::Util::Trace
    Legacy wrapper for Test2::EventFacet::Trace.

Test2::V0
    0Th edition of the Test2 recommended bundle.

Test2::Workflow
    A test workflow is a way of structuring tests using

Test2::Workflow::BlockBase
    Base class for all workflow blocks.

Test2::Workflow::Build
    Represents a build in progress.

Test2::Workflow::Runner
    Runs the workflows.

Test2::Workflow::Task
    Encapsulation of a Task

Test2::Workflow::Task::Action
    Encapsulation of an action.

Test2::Workflow::Task::Group
    Encapsulation of a group (describe).

Test::Builder
    Backend for building test libraries

Test::Builder::Formatter
    Test::Builder subclass of Test2::Formatter::TAP

Test::Builder::Module
    Base class for test modules

Test::Builder::Tester
    Test testsuites that have been built with

Test::Builder::Tester::Color
    Turn on colour in Test::Builder::Tester

Test::Builder::TodoDiag
    Test::Builder subclass of Test2::Event::Diag

Test::Harness
    Run Perl standard test scripts with statistics

Test::Harness::Beyond
    Beyond make test

Test::More
    Yet another framework for writing test scripts

Test::Simple
    Basic utilities for writing tests.

Test::Tester
    Ease testing test modules built with Test::Builder

Test::Tester::Capture
    Help testing test modules built with Test::Builder

Test::Tester::CaptureRunner
    Help testing test modules built with Test::Builder

Test::Tutorial
    A tutorial about writing really basic tests

Test::use::ok
    Alternative to Test::More::use_ok

Text::Abbrev
    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::Tabs
    Expand and unexpand tabs like 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

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::Hash::NamedCapture
    Named regexp capture buffers

Tie::Memoize
    Add data to hash when needed

Tie::RefHash
    Use references as hash keys

Tie::Scalar
    Base class definitions for tied scalars

Tie::StdHandle
    Base class definitions for tied handles

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::Piece
    Object Oriented time objects

Time::Seconds
    A simple API to convert seconds to other date values

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::Collate::CJK::Big5
    Weighting CJK Unified Ideographs

Unicode::Collate::CJK::GB2312
    Weighting CJK Unified Ideographs

Unicode::Collate::CJK::JISX0208
    Weighting JIS KANJI for Unicode::Collate

Unicode::Collate::CJK::Korean
    Weighting CJK Unified Ideographs

Unicode::Collate::CJK::Pinyin
    Weighting CJK Unified Ideographs

Unicode::Collate::CJK::Stroke
    Weighting CJK Unified Ideographs

Unicode::Collate::CJK::Zhuyin
    Weighting CJK Unified Ideographs

Unicode::Collate::Locale
    Linguistic tailoring for DUCET via Unicode::Collate

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

VMS::DCLsym
    Perl extension to manipulate DCL symbols

VMS::Filespec
    Convert between VMS and Unix file specification syntax

VMS::Stdio
    Standard I/O functions via VMS extensions

Win32
    Interfaces to some Win32 API Functions

Win32API::File
    Low-level access to Win32 system API calls for files/dirs.

Win32CORE
    Win32 CORE function stubs

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

autodie::Scope::Guard
    Wrapper class for calling subs at end of scope

autodie::Scope::GuardStack
    Hook stack for managing scopes via %^H

autodie::Util
    Internal Utility subroutines for autodie and Fatal

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).

    % 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 @INC from being populated by "PERL5LIB", "PERLLIB", and "PERL_USE_UNSAFE_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 Google or DuckDuckGo.

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 https://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

You can find the CPAN online at <https://www.cpan.org/>

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, perlobj, and AutoLoader for details about the AUTOLOAD mechanism.

  Guidelines for Module Creation

•   Do similar modules already exist in some form?

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

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

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

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

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

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

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

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

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

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

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

    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: "$obj = YOURCLASS->new();" into: "$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:

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

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

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

•   Select what to export.

    Do NOT export method names!

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

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

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

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

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

•   Select a name for the module.

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

    Having 57 modules all called Sort will not make life easy for anyone (though having 23 called Sort::Quick is only marginally better :-). Imagine someone trying to install your module alongside many others.

    If 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.

    For additional guidance on the naming of modules, please consult:

        https://pause.perl.org/pause/query?ACTION=pause_namingmodules

    or send mail to the <module-authors@perl.org> mailing list.

•   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. The <module-authors@perl.org> mailing list is useful for this purpose; it's also accessible via news interface as perl.module-authors at nntp.perl.org.

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

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

•   README and other Additional Files.

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

    •   A description of the module/package/extension etc.

    •   A copyright notice - see below.

    •   Prerequisites - what else you may need to have.

    •   How to build it - possible changes to Makefile.PL etc.

    •   How to install it.

    •   Recent changes in this release, especially incompatibilities

    •   Changes / enhancements you plan to make in the future.

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

    •   Adding a Copyright Notice.

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

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

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

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

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

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

        To be fully compatible with the Exporter and MakeMaker modules you should store your module's version number in a non-my package variable called $VERSION. This should be a positive floating point number with at least two digits after the decimal (i.e., hundredths, e.g., "$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.

        If possible, register the module with CPAN. Follow the instructions and links on:

           https://www.cpan.org/modules/04pause.html

        and upload to:

           https://pause.perl.org/

        and notify <modules@perl.org>. This will allow anyone to install your module using the "cpan" tool distributed with Perl.

        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!

    •   Take care when changing a released module.

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

  Guidelines for Converting Perl 4 Library Scripts into Modules

•   There is no requirement to convert anything.

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

•   Consider the implications.

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

•   Make the most of the opportunity.

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

•   The pl2pm utility will get you started.

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

    •   Adds the standard Module prologue lines

    •   Converts package specifiers from ' to ::

    •   Converts die(...) to croak(...)

    •   Several other minor changes

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

  Guidelines for Reusing Application Code

•   Complete applications rarely belong in the Perl Module Library.

•   Many applications contain some Perl code that could be reused.

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

•   Break-out the reusable code into one or more separate module files.

•   Take the opportunity to reconsider and redesign the interfaces.

•   In some cases the 'application' can then be reduced to a small

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

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

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

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