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NAME ^

perlmodlib - constructing new Perl modules and finding existing ones

DESCRIPTION ^

THE PERL MODULE LIBRARY ^

Many modules are included the Perl distribution. These are described below, and all end in .pm. You may discover compiled library file (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

autouse

Postpone load of modules until a function is used

base

Establish IS-A relationship with base class at compile time

blib

Use MakeMaker's uninstalled version of a package

bytes

Force byte semantics rather than character semantics

charnames

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

constant

Declare constants

diagnostics

Perl compiler pragma to force verbose warning diagnostics

encoding

Pragma to control the conversion of legacy data into Unicode

fields

Compile-time class fields

filetest

Control the filetest permission operators

integer

Use integer arithmetic instead of floating point

less

Request less of something from the compiler

locale

Use and avoid POSIX locales for built-in operations

open

Set default disciplines for input and output

overload

Package for overloading perl operations

sigtrap

Enable simple signal handling

sort

Control sort() behaviour

strict

Restrict unsafe constructs

subs

Predeclare sub names

utf8

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

vars

Predeclare global variable names (obsolete)

vmsish

Control VMS-specific language features

warnings

Control optional warnings

warnings::register

Warnings import function

Standard Modules

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

AnyDBM_File

Provide framework for multiple DBMs

Attribute::Handlers

Simpler definition of attribute handlers

AutoLoader

Load subroutines only on demand

AutoSplit

Split a package for autoloading

Benchmark

Benchmark running times of Perl code

CGI

Simple Common Gateway Interface Class

CGI::Apache

Backward compatibility module for CGI.pm

CGI::Carp

CGI routines for writing to the HTTPD (or other) error log

CGI::Cookie

Interface to Netscape Cookies

CGI::Fast

CGI Interface for Fast CGI

CGI::Pretty

Module to produce nicely formatted HTML code

CGI::Push

Simple Interface to Server Push

CGI::Switch

Backward compatibility module for defunct CGI::Switch

CGI::Util

Internal utilities used by CGI module

CPAN

Query, download and build perl modules from CPAN sites

CPAN::FirstTime

Utility for CPAN::Config file Initialization

CPAN::Nox

Wrapper around CPAN.pm without using any XS module

Carp

Warn of errors (from perspective of caller)

Carp::Heavy

No user serviceable parts inside

Class::ISA

Report the search path for a class's ISA tree

Class::Struct

Declare struct-like datatypes as Perl classes

Cwd

Get pathname of current working directory

DB

Programmatic interface to the Perl debugging API (draft, subject to

Devel::SelfStubber

Generate stubs for a SelfLoading module

Digest

Modules that calculate message digests

DirHandle

Supply object methods for directory handles

Dumpvalue

Provides screen dump of Perl data.

English

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

Env

Perl module that imports environment variables as scalars or arrays

Exporter

Implements default import method for modules

Exporter::Heavy

Exporter guts

ExtUtils::Command

Utilities to replace common UNIX commands in Makefiles etc.

ExtUtils::Constant

Generate XS code to import C header constants

ExtUtils::Embed

Utilities for embedding Perl in C/C++ applications

ExtUtils::Install

Install files from here to there

ExtUtils::Installed

Inventory management of installed modules

ExtUtils::Liblist

Determine libraries to use and how to use them

ExtUtils::MM_Cygwin

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

ExtUtils::MM_NW5

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

ExtUtils::MM_OS2

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

ExtUtils::MM_Unix

Methods used by ExtUtils::MakeMaker

ExtUtils::MM_VMS

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

ExtUtils::MM_Win32

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

ExtUtils::MakeMaker

Create an extension Makefile

ExtUtils::Manifest

Utilities to write and check a MANIFEST file

ExtUtils::Mkbootstrap

Make a bootstrap file for use by DynaLoader

ExtUtils::Mksymlists

Write linker options files for dynamic extension

ExtUtils::Packlist

Manage .packlist files

ExtUtils::testlib

Add blib/* directories to @INC

Fatal

Replace functions with equivalents which succeed or die

File::Basename

Split a pathname into pieces

File::CheckTree

Run many filetest checks on a tree

File::Compare

Compare files or filehandles

File::Copy

Copy files or filehandles

File::DosGlob

DOS like globbing and then some

File::Find

Traverse a file tree

File::Path

Create or remove directory trees

File::Spec

Portably perform operations on file names

File::Spec::Cygwin

Methods for Cygwin file specs

File::Spec::Epoc

Methods for Epoc file specs

File::Spec::Functions

Portably perform operations on file names

File::Spec::Mac

File::Spec for Mac OS (Classic)

File::Spec::OS2

Methods for OS/2 file specs

File::Spec::Unix

File::Spec for Unix, base for other File::Spec modules

File::Spec::VMS

Methods for VMS file specs

File::Spec::Win32

Methods for Win32 file specs

File::Temp

Return name and handle of a temporary file safely

File::stat

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

FileCache

Keep more files open than the system permits

FileHandle

Supply object methods for filehandles

Filter::Simple

Simplified source filtering

FindBin

Locate directory of original perl script

Getopt::Long

Extended processing of command line options

Getopt::Std

Process single-character switches with switch clustering

I18N::Collate

Compare 8-bit scalar data according to the current locale

I18N::LangTags

Functions for dealing with RFC3066-style language tags

I18N::LangTags::List

Tags and names for human languages

IPC::Open2

Open a process for both reading and writing

IPC::Open3

Open a process for reading, writing, and error handling

Locale::Constants

Constants for Locale codes

Locale::Country

ISO codes for country identification (ISO 3166)

Locale::Currency

ISO three letter codes for currency identification (ISO 4217)

Locale::Language

ISO two letter codes for language identification (ISO 639)

Locale::Maketext

Framework for localization

Locale::Maketext::TPJ13

Article about software localization

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::Complex

Complex numbers and associated mathematical functions

Math::Trig

Trigonometric functions

Memoize

Make your functions faster by trading space for time

Memoize::AnyDBM_File

Glue to provide EXISTS for AnyDBM_File for Storable use

Memoize::Expire

Plug-in module for automatic expiration of memoized values

Memoize::ExpireFile

Test for Memoize expiration semantics

Memoize::ExpireTest

Test for Memoize expiration semantics

Memoize::NDBM_File

Glue to provide EXISTS for NDBM_File for Storable use

Memoize::SDBM_File

Glue to provide EXISTS for SDBM_File for Storable use

Memoize::Storable

Store Memoized data in Storable database

NEXT

Provide a pseudo-class NEXT that allows method redispatch

Net::Cmd

Network Command class (as used by FTP, SMTP etc)

Net::Config

Local configuration data for libnet

Net::Domain

Attempt to evaluate the current host's internet name and domain

Net::FTP

FTP Client class

Net::NNTP

NNTP Client class

Net::Netrc

OO interface to users netrc file

Net::POP3

Post Office Protocol 3 Client class (RFC1081)

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

PerlIO

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

Pod::Checker

Check pod documents for syntax errors

Pod::Find

Find POD documents in directory trees

Pod::Functions

Group Perl's functions a la perlfunc.pod

Pod::Html

Module to convert pod files to HTML

Pod::InputObjects

Objects representing POD input paragraphs, commands, etc.

Pod::LaTeX

Convert Pod data to formatted Latex

Pod::Man

Convert POD data to formatted *roff input

Pod::ParseLink

Parse an L<> formatting code in POD text

Pod::ParseUtils

Helpers for POD parsing and conversion

Pod::Parser

Base class for creating POD filters and translators

Pod::Plainer

Perl extension for converting Pod to old style Pod.

Pod::Select

Extract selected sections of POD from input

Pod::Text

Convert POD data to formatted ASCII text

Pod::Text::Color

Convert POD data to formatted color ASCII text

Pod::Text::Overstrike

Convert POD data to formatted overstrike text

Pod::Text::Termcap

Convert POD data to ASCII text with format escapes

Pod::Usage

Print a usage message from embedded pod documentation

Pod::t::basic

Test of various basic POD features in translators.

Search::Dict

Search for key in dictionary file

SelectSaver

Save and restore selected file handle

SelfLoader

Load functions only on demand

Shell

Run shell commands transparently within perl

Switch

A switch statement for Perl

Symbol

Manipulate Perl symbols and their names

Term::ANSIColor

Color screen output using ANSI escape sequences

Term::Cap

Perl termcap interface

Term::Complete

Perl word completion module

Term::ReadLine

Perl interface to various readline packages. If

Test

Provides a simple framework for writing test scripts

Test::Builder

Backend for building test libraries

Test::Harness

Run perl standard test scripts with statistics

Test::More

Yet another framework for writing test scripts

Test::Simple

Basic utilities for writing tests.

Test::Tutorial

A tutorial about writing really basic tests

Text::Abbrev

Create an abbreviation table from a list

Text::Balanced

Extract delimited text sequences from strings.

Text::ParseWords

Parse text into an array of tokens or array of arrays

Text::Soundex

Implementation of the Soundex Algorithm as Described by Knuth

Text::Tabs

Expand and unexpand tabs per the unix expand(1) and unexpand(1)

Text::Wrap

Line wrapping to form simple paragraphs

Thread

Manipulate threads in Perl

Tie::Array

Base class for tied arrays

Tie::Handle

Base class definitions for tied handles

Tie::Hash

Base class definitions for tied hashes

Tie::RefHash

Use references as hash keys

Tie::Scalar

Base class definitions for tied scalars

Tie::SubstrHash

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

Time::Local

Efficiently compute time from local and GMT time

Time::gmtime

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

Time::localtime

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

Time::tm

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

UNIVERSAL

Base class for ALL classes (blessed references)

Unicode::Collate

Use UCA (Unicode Collation Algorithm)

Unicode::UCD

Unicode character database

User::grent

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

User::pwent

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

Win32

Interfaces to some Win32 API Functions

To find out all modules installed on your system, including those without documentation or outside the standard release, just do this:

    % find `perl -e 'print "@INC"'` -name '*.pm' -print

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.

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 Deja News.

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:

Registered CPAN sites as of this writing include the following. You should try to choose one close to you:

Africa

Asia

Central America

Europe

North America

Oceania

South America

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

Guidelines for Converting Perl 4 Library Scripts into Modules

Guidelines for Reusing Application Code

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.

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