3 perlmodlib - constructing new Perl modules and finding existing ones
7 =head1 THE PERL MODULE LIBRARY
9 A number of modules are included the Perl distribution. These are
10 described below, and all end in F<.pm>. You may also discover files in
11 the library directory that end in either F<.pl> or F<.ph>. These are old
12 libraries supplied so that old programs that use them still run. The
13 F<.pl> files will all eventually be converted into standard modules, and
14 the F<.ph> files made by B<h2ph> will probably end up as extension modules
15 made by B<h2xs>. (Some F<.ph> values may already be available through the
16 POSIX module.) The B<pl2pm> file in the distribution may help in your
17 conversion, but it's just a mechanical process and therefore far from
20 =head2 Pragmatic Modules
22 They work somewhat like pragmas in that they tend to affect the compilation of
23 your program, and thus will usually work well only when used within a
24 C<use>, or C<no>. Most of these are lexically scoped, so an inner BLOCK
25 may countermand any of these by saying:
30 which lasts until the end of that BLOCK.
32 Unlike the pragmas that effect the C<$^H> hints variable, the C<use
33 vars> and C<use subs> declarations are not BLOCK-scoped. They allow
34 you to predeclare a variables or subroutines within a particular
35 I<file> rather than just a block. Such declarations are effective
36 for the entire file for which they were declared. You cannot rescind
37 them with C<no vars> or C<no subs>.
39 The following pragmas are defined (and have their own documentation).
43 =item use autouse MODULE => qw(sub1 sub2 sub3)
45 Defers C<require MODULE> until someone calls one of the specified
46 subroutines (which must be exported by MODULE). This pragma should be
47 used with caution, and only when necessary.
51 manipulate @INC at compile time to use MakeMaker's uninstalled version
56 force verbose warning diagnostics
60 compute arithmetic in integer instead of double
64 request less of something from the compiler
68 manipulate @INC at compile time
72 use or ignore current locale for builtin operations (see L<perllocale>)
76 restrict named opcodes when compiling or running Perl code
80 overload basic Perl operations
84 alter behaviour of regular expressions
88 enable simple signal handling
92 restrict unsafe constructs
100 adopt certain VMS-specific behaviors
104 predeclare global variable names
108 =head2 Standard Modules
110 Standard, bundled modules are all expected to behave in a well-defined
111 manner with respect to namespace pollution because they use the
112 Exporter module. See their own documentation for details.
118 provide framework for multiple DBMs
122 load functions only on demand
126 split a package for autoloading
130 benchmark running times of code
134 interface to Comprehensive Perl Archive Network
136 =item CPAN::FirstTime
138 create a CPAN configuration file
142 run CPAN while avoiding compiled extensions
146 warn of errors (from perspective of caller)
150 declare struct-like datatypes
154 access Perl configuration information
158 get pathname of current working directory
162 access to Berkeley DB
164 =item Devel::SelfStubber
166 generate stubs for a SelfLoading module
170 supply object methods for directory handles
174 dynamically load C libraries into Perl code
178 use nice English (or awk) names for ugly punctuation variables
182 import environment variables
186 implements default import method for modules
188 =item ExtUtils::Embed
190 utilities for embedding Perl in C/C++ applications
192 =item ExtUtils::Install
194 install files from here to there
196 =item ExtUtils::Liblist
198 determine libraries to use and how to use them
200 =item ExtUtils::MM_OS2
202 methods to override Unix behaviour in ExtUtils::MakeMaker
204 =item ExtUtils::MM_Unix
206 methods used by ExtUtils::MakeMaker
208 =item ExtUtils::MM_VMS
210 methods to override Unix behaviour in ExtUtils::MakeMaker
212 =item ExtUtils::MakeMaker
214 create an extension Makefile
216 =item ExtUtils::Manifest
218 utilities to write and check a MANIFEST file
220 =item ExtUtils::Mkbootstrap
222 make a bootstrap file for use by DynaLoader
224 =item ExtUtils::Mksymlists
226 write linker options files for dynamic extension
228 =item ExtUtils::testlib
230 add blib/* directories to @INC
234 make errors in builtins or Perl functions fatal
238 load the C Fcntl.h defines
242 split a pathname into pieces
244 =item File::CheckTree
246 run many filetest checks on a tree
250 compare files or filehandles
254 copy files or filehandles
262 create or remove a series of directories
266 portably perform operations on file names
268 =item File::Spec::Functions
270 function call interface to File::Spec module
274 by-name interface to Perl's builtin stat() functions
278 keep more files open than the system permits
282 supply object methods for filehandles
286 locate directory of original Perl script
290 access to the gdbm library
294 extended processing of command line options
298 process single-character switches with switch clustering
302 compare 8-bit scalar data according to the current locale
306 load various IO modules
310 supply object methods for filehandles
314 supply object methods for I/O handles
318 supply object methods for pipes
322 supply seek based methods for I/O objects
326 OO interface to the select system call
330 object interface to socket communications
334 open a process for both reading and writing
338 open a process for reading, writing, and error handling
342 arbitrary length float math package
346 arbitrary size integer math package
350 complex numbers and associated mathematical functions
354 simple interface to parts of Math::Complex for those who
355 need trigonometric functions only for real numbers
359 tied access to ndbm files
367 by-name interface to Perl's builtin gethost*() functions
371 by-name interface to Perl's builtin getnet*() functions
375 by-name interface to Perl's builtin getproto*() functions
379 by-name interface to Perl's builtin getserv*() functions
383 disable named opcodes when compiling or running Perl code
387 convert POD data to formatted ASCII text
391 interface to IEEE Standard 1003.1
395 tied access to sdbm files
399 compile and execute code in restricted compartments
403 search for key in dictionary file
407 save and restore selected file handle
411 load functions only on demand
415 run shell commands transparently within Perl
419 load the C socket.h defines and structure manipulators
423 manipulate Perl symbols and their names
427 try every conceivable way to get hostname
431 interface to the Unix syslog(3) calls
439 word completion module
443 interface to various C<readline> packages
447 run Perl standard test scripts with statistics
451 create an abbreviation table from a list
453 =item Text::ParseWords
455 parse text into an array of tokens
459 implementation of the Soundex Algorithm as described by Knuth
463 expand and unexpand tabs per the Unix expand(1) and unexpand(1)
467 line wrapping to form simple paragraphs
471 base class definitions for tied hashes
475 base class definitions for tied hashes with references as keys
479 base class definitions for tied scalars
481 =item Tie::SubstrHash
483 fixed-table-size, fixed-key-length hashing
487 efficiently compute time from local and GMT time
491 by-name interface to Perl's builtin gmtime() function
493 =item Time::localtime
495 by-name interface to Perl's builtin localtime() function
499 internal object used by Time::gmtime and Time::localtime
503 base class for ALL classes (blessed references)
507 by-name interface to Perl's builtin getgr*() functions
511 by-name interface to Perl's builtin getpw*() functions
515 To find out I<all> the modules installed on your system, including
516 those without documentation or outside the standard release, do this:
518 % find `perl -e 'print "@INC"'` -name '*.pm' -print
520 They should all have their own documentation installed and accessible via
521 your system man(1) command. If that fails, try the I<perldoc> program.
523 =head2 Extension Modules
525 Extension modules are written in C (or a mix of Perl and C) and may be
526 statically linked or in general are
527 dynamically loaded into Perl if and when you need them. Supported
528 extension modules include the Socket, Fcntl, and POSIX modules.
530 Many popular C extension modules do not come bundled (at least, not
531 completely) due to their sizes, volatility, or simply lack of time for
532 adequate testing and configuration across the multitude of platforms on
533 which Perl was beta-tested. You are encouraged to look for them in
534 archie(1L), the Perl FAQ or Meta-FAQ, the WWW page, and even with their
535 authors before randomly posting asking for their present condition and
540 CPAN stands for the Comprehensive Perl Archive Network. This is a globally
541 replicated collection of all known Perl materials, including hundreds
542 of unbundled modules. Here are the major categories of modules:
547 Language Extensions and Documentation Tools
553 Operating System Interfaces
556 Networking, Device Control (modems) and InterProcess Communication
559 Data Types and Data Type Utilities
568 Interfaces to / Emulations of Other Programming Languages
571 File Names, File Systems and File Locking (see also File Handles)
574 String Processing, Language Text Processing, Parsing, and Searching
577 Option, Argument, Parameter, and Configuration File Processing
580 Internationalization and Locale
583 Authentication, Security, and Encryption
586 World Wide Web, HTML, HTTP, CGI, MIME
589 Server and Daemon Utilities
592 Archiving and Compression
595 Images, Pixmap and Bitmap Manipulation, Drawing, and Graphing
601 Control Flow Utilities (callbacks and exceptions etc)
604 File Handle and Input/Output Stream Utilities
607 Miscellaneous Modules
611 The registered CPAN sites as of this writing include the following.
612 You should try to choose one close to you:
619 South Africa ftp://ftp.is.co.za/programming/perl/CPAN/
620 ftp://ftpza.co.za/pub/mirrors/cpan/
625 Armenia ftp://sunsite.aua.am/pub/CPAN/
626 China ftp://freesoft.cei.gov.cn/pub/languages/perl/CPAN/
627 Hong Kong ftp://ftp.hkstar.com/pub/CPAN/
628 Israel ftp://bioinfo.weizmann.ac.il/pub/software/perl/CPAN/
629 Japan ftp://ftp.dti.ad.jp/pub/lang/CPAN/
630 ftp://ftp.jaist.ac.jp/pub/lang/perl/CPAN/
631 ftp://ftp.lab.kdd.co.jp/lang/perl/CPAN/
632 ftp://ftp.meisei-u.ac.jp/pub/CPAN/
633 ftp://mirror.nucba.ac.jp/mirror/Perl/
634 Singapore ftp://ftp.nus.edu.sg/pub/unix/perl/CPAN/
635 South Korea ftp://ftp.bora.net/pub/CPAN/
636 ftp://ftp.nuri.net/pub/CPAN/
637 Taiwan ftp://ftp.wownet.net/pub2/PERL/
638 ftp://ftp1.sinica.edu.tw/pub1/perl/CPAN/
639 Thailand ftp://ftp.cs.riubon.ac.th/pub/mirrors/CPAN/
640 ftp://ftp.nectec.or.th/pub/mirrors/CPAN/
645 Australia ftp://cpan.topend.com.au/pub/CPAN/
646 ftp://ftp.labyrinth.net.au/pub/perl/CPAN/
647 ftp://ftp.sage-au.org.au/pub/compilers/perl/CPAN/
648 ftp://mirror.aarnet.edu.au/pub/perl/CPAN/
649 New Zealand ftp://ftp.auckland.ac.nz/pub/perl/CPAN/
650 ftp://sunsite.net.nz/pub/languages/perl/CPAN/
655 Costa Rica ftp://ftp.ucr.ac.cr/pub/Unix/CPAN/
660 Austria ftp://ftp.tuwien.ac.at/pub/languages/perl/CPAN/
661 Belgium ftp://ftp.kulnet.kuleuven.ac.be/pub/mirror/CPAN/
662 Bulgaria ftp://ftp.ntrl.net/pub/mirrors/CPAN/
663 Croatia ftp://ftp.linux.hr/pub/CPAN/
664 Czech Republic ftp://ftp.fi.muni.cz/pub/perl/
665 ftp://sunsite.mff.cuni.cz/Languages/Perl/CPAN/
666 Denmark ftp://sunsite.auc.dk/pub/languages/perl/CPAN/
667 Estonia ftp://ftp.ut.ee/pub/languages/perl/CPAN/
668 Finland ftp://ftp.funet.fi/pub/languages/perl/CPAN/
669 France ftp://ftp.lip6.fr/pub/perl/CPAN/
670 ftp://ftp.oleane.net/pub/mirrors/CPAN/
671 ftp://ftp.pasteur.fr/pub/computing/CPAN/
672 Germany ftp://ftp.archive.de.uu.net/pub/CPAN/
673 ftp://ftp.gmd.de/packages/CPAN/
674 ftp://ftp.gwdg.de/pub/languages/perl/CPAN/
675 ftp://ftp.leo.org/pub/comp/programming/languages/script/perl/CPAN/
676 ftp://ftp.mpi-sb.mpg.de/pub/perl/CPAN/
677 ftp://ftp.rz.ruhr-uni-bochum.de/pub/CPAN/
678 ftp://ftp.uni-erlangen.de/pub/source/CPAN/
679 ftp://ftp.uni-hamburg.de/pub/soft/lang/perl/CPAN/
680 Greece ftp://ftp.ntua.gr/pub/lang/perl/
681 Hungary ftp://ftp.kfki.hu/pub/packages/perl/CPAN/
682 Ireland ftp://sunsite.compapp.dcu.ie/pub/perl/
683 Italy ftp://cis.uniRoma2.it/CPAN/
684 ftp://ftp.flashnet.it/pub/CPAN/
685 ftp://ftp.unipi.it/pub/mirror/perl/CPAN/
686 Netherlands ftp://ftp.cs.uu.nl/mirror/CPAN/
687 ftp://ftp.nluug.nl/pub/languages/perl/CPAN/
688 Norway ftp://ftp.uit.no/pub/languages/perl/cpan/
689 ftp://sunsite.uio.no/pub/languages/perl/CPAN/
690 Poland ftp://ftp.man.szczecin.pl/pub/perl/CPAN/
691 ftp://ftp.man.torun.pl/pub/doc/CPAN/
692 ftp://ftp.pk.edu.pl/pub/lang/perl/CPAN/
693 ftp://sunsite.icm.edu.pl/pub/CPAN/
694 Portugal ftp://ftp.ci.uminho.pt/pub/mirrors/cpan/
695 ftp://ftp.ua.pt/pub/CPAN/
696 Romania ftp://ftp.dntis.ro/pub/mirrors/perl-cpan/
697 ftp://ftp.dnttm.ro/pub/CPAN/
698 Russia ftp://cpan.npi.msu.su/CPAN/
699 ftp://ftp.sai.msu.su/pub/lang/perl/CPAN/
700 Slovakia ftp://ftp.entry.sk/pub/languages/perl/CPAN/
701 Slovenia ftp://ftp.arnes.si/software/perl/CPAN/
702 Spain ftp://ftp.etse.urv.es/pub/perl/
703 ftp://ftp.rediris.es/mirror/CPAN/
704 Sweden ftp://ftp.sunet.se/pub/lang/perl/CPAN/
705 Switzerland ftp://sunsite.cnlab-switch.ch/mirror/CPAN/
706 Turkey ftp://sunsite.bilkent.edu.tr/pub/languages/CPAN/
707 United Kingdom ftp://ftp.demon.co.uk/pub/mirrors/perl/CPAN/
708 ftp://ftp.flirble.org/pub/languages/perl/CPAN/
709 ftp://ftp.plig.org/pub/CPAN/
710 ftp://sunsite.doc.ic.ac.uk/packages/CPAN/
711 ftp://unix.hensa.ac.uk/mirrors/perl-CPAN/
716 Alberta ftp://sunsite.ualberta.ca/pub/Mirror/CPAN/
717 California ftp://ftp.cdrom.com/pub/perl/CPAN/
718 ftp://ftp.digital.com/pub/plan/perl/CPAN/
719 Colorado ftp://ftp.cs.colorado.edu/pub/perl/CPAN/
720 Florida ftp://ftp.cise.ufl.edu/pub/perl/CPAN/
721 Illinois ftp://uiarchive.uiuc.edu/pub/lang/perl/CPAN/
722 Indiana ftp://csociety-ftp.ecn.purdue.edu/pub/CPAN/
723 ftp://ftp.uwsg.indiana.edu/pub/perl/CPAN/
724 Manitoba ftp://theory.uwinnipeg.ca/pub/CPAN/
725 Massachusetts ftp://ftp.ccs.neu.edu/net/mirrors/ftp.funet.fi/pub/languages/perl/CPAN/
726 ftp://ftp.iguide.com/pub/mirrors/packages/perl/CPAN/
727 Mexico D.F. ftp://ftp.msg.com.mx/pub/CPAN/
728 New York ftp://ftp.rge.com/pub/languages/perl/
729 North Carolina ftp://ftp.duke.edu/pub/perl/
730 Oklahoma ftp://ftp.ou.edu/mirrors/CPAN/
731 Ontario ftp://ftp.crc.ca/pub/packages/perl/CPAN/
732 Oregon ftp://ftp.orst.edu/pub/packages/CPAN/
733 Pennsylvania ftp://ftp.epix.net/pub/languages/perl/
734 Texas ftp://ftp.sedl.org/pub/mirrors/CPAN/
735 Utah ftp://mirror.xmission.com/CPAN/
736 Virginia ftp://ftp.perl.org/pub/perl/CPAN/
737 ftp://ruff.cs.jmu.edu/pub/CPAN/
738 Washington ftp://ftp.spu.edu/pub/CPAN/
743 Brazil ftp://cpan.if.usp.br/pub/mirror/CPAN/
744 Chile ftp://ftp.ing.puc.cl/pub/unix/perl/CPAN/
745 ftp://sunsite.dcc.uchile.cl/pub/Lang/perl/CPAN/
749 For an up-to-date listing of CPAN sites,
750 see F<http://www.perl.com/perl/CPAN> or F<ftp://ftp.perl.com/perl/>.
752 =head1 Modules: Creation, Use, and Abuse
754 (The following section is borrowed directly from Tim Bunce's modules
755 file, available at your nearest CPAN site.)
757 Perl implements a class using a package, but the presence of a
758 package doesn't imply the presence of a class. A package is just a
759 namespace. A class is a package that provides subroutines that can be
760 used as methods. A method is just a subroutine that expects, as its
761 first argument, either the name of a package (for "static" methods),
762 or a reference to something (for "virtual" methods).
764 A module is a file that (by convention) provides a class of the same
765 name (sans the .pm), plus an import method in that class that can be
766 called to fetch exported symbols. This module may implement some of
767 its methods by loading dynamic C or C++ objects, but that should be
768 totally transparent to the user of the module. Likewise, the module
769 might set up an AUTOLOAD function to slurp in subroutine definitions on
770 demand, but this is also transparent. Only the F<.pm> file is required to
771 exist. See L<perlsub>, L<perltoot>, and L<AutoLoader> for details about
772 the AUTOLOAD mechanism.
774 =head2 Guidelines for Module Creation
778 =item Do similar modules already exist in some form?
780 If so, please try to reuse the existing modules either in whole or
781 by inheriting useful features into a new class. If this is not
782 practical try to get together with the module authors to work on
783 extending or enhancing the functionality of the existing modules.
784 A perfect example is the plethora of packages in perl4 for dealing
785 with command line options.
787 If you are writing a module to expand an already existing set of
788 modules, please coordinate with the author of the package. It
789 helps if you follow the same naming scheme and module interaction
790 scheme as the original author.
792 =item Try to design the new module to be easy to extend and reuse.
794 Use blessed references. Use the two argument form of bless to bless
795 into the class name given as the first parameter of the constructor,
800 return bless {}, $class;
803 or even this if you'd like it to be used as either a static
808 my $class = ref($self) || $self;
809 return bless {}, $class;
812 Pass arrays as references so more parameters can be added later
813 (it's also faster). Convert functions into methods where
814 appropriate. Split large methods into smaller more flexible ones.
815 Inherit methods from other modules if appropriate.
817 Avoid class name tests like: C<die "Invalid" unless ref $ref eq 'FOO'>.
818 Generally you can delete the "C<eq 'FOO'>" part with no harm at all.
819 Let the objects look after themselves! Generally, avoid hard-wired
820 class names as far as possible.
822 Avoid C<$r-E<gt>Class::func()> where using C<@ISA=qw(... Class ...)> and
823 C<$r-E<gt>func()> would work (see L<perlbot> for more details).
825 Use autosplit so little used or newly added functions won't be a
826 burden to programs that don't use them. Add test functions to
827 the module after __END__ either using AutoSplit or by saying:
829 eval join('',<main::DATA>) || die $@ unless caller();
831 Does your module pass the 'empty subclass' test? If you say
832 "C<@SUBCLASS::ISA = qw(YOURCLASS);>" your applications should be able
833 to use SUBCLASS in exactly the same way as YOURCLASS. For example,
834 does your application still work if you change: C<$obj = new YOURCLASS;>
835 into: C<$obj = new SUBCLASS;> ?
837 Avoid keeping any state information in your packages. It makes it
838 difficult for multiple other packages to use yours. Keep state
839 information in objects.
841 Always use B<-w>. Try to C<use strict;> (or C<use strict qw(...);>).
842 Remember that you can add C<no strict qw(...);> to individual blocks
843 of code that need less strictness. Always use B<-w>. Always use B<-w>!
844 Follow the guidelines in the perlstyle(1) manual.
846 =item Some simple style guidelines
848 The perlstyle manual supplied with Perl has many helpful points.
850 Coding style is a matter of personal taste. Many people evolve their
851 style over several years as they learn what helps them write and
852 maintain good code. Here's one set of assorted suggestions that
853 seem to be widely used by experienced developers:
855 Use underscores to separate words. It is generally easier to read
856 $var_names_like_this than $VarNamesLikeThis, especially for
857 non-native speakers of English. It's also a simple rule that works
858 consistently with VAR_NAMES_LIKE_THIS.
860 Package/Module names are an exception to this rule. Perl informally
861 reserves lowercase module names for 'pragma' modules like integer
862 and strict. Other modules normally begin with a capital letter and
863 use mixed case with no underscores (need to be short and portable).
865 You may find it helpful to use letter case to indicate the scope
866 or nature of a variable. For example:
868 $ALL_CAPS_HERE constants only (beware clashes with Perl vars)
869 $Some_Caps_Here package-wide global/static
870 $no_caps_here function scope my() or local() variables
872 Function and method names seem to work best as all lowercase.
873 e.g., C<$obj-E<gt>as_string()>.
875 You can use a leading underscore to indicate that a variable or
876 function should not be used outside the package that defined it.
878 =item Select what to export.
880 Do NOT export method names!
882 Do NOT export anything else by default without a good reason!
884 Exports pollute the namespace of the module user. If you must
885 export try to use @EXPORT_OK in preference to @EXPORT and avoid
886 short or common names to reduce the risk of name clashes.
888 Generally anything not exported is still accessible from outside the
889 module using the ModuleName::item_name (or C<$blessed_ref-E<gt>method>)
890 syntax. By convention you can use a leading underscore on names to
891 indicate informally that they are 'internal' and not for public use.
893 (It is actually possible to get private functions by saying:
894 C<my $subref = sub { ... }; &$subref;>. But there's no way to call that
895 directly as a method, because a method must have a name in the symbol
898 As a general rule, if the module is trying to be object oriented
899 then export nothing. If it's just a collection of functions then
900 @EXPORT_OK anything but use @EXPORT with caution.
902 =item Select a name for the module.
904 This name should be as descriptive, accurate, and complete as
905 possible. Avoid any risk of ambiguity. Always try to use two or
906 more whole words. Generally the name should reflect what is special
907 about what the module does rather than how it does it. Please use
908 nested module names to group informally or categorize a module.
909 There should be a very good reason for a module not to have a nested name.
910 Module names should begin with a capital letter.
912 Having 57 modules all called Sort will not make life easy for anyone
913 (though having 23 called Sort::Quick is only marginally better :-).
914 Imagine someone trying to install your module alongside many others.
915 If in any doubt ask for suggestions in comp.lang.perl.misc.
917 If you are developing a suite of related modules/classes it's good
918 practice to use nested classes with a common prefix as this will
919 avoid namespace clashes. For example: Xyz::Control, Xyz::View,
920 Xyz::Model etc. Use the modules in this list as a naming guide.
922 If adding a new module to a set, follow the original author's
923 standards for naming modules and the interface to methods in
926 To be portable each component of a module name should be limited to
927 11 characters. If it might be used on MS-DOS then try to ensure each is
928 unique in the first 8 characters. Nested modules make this easier.
930 =item Have you got it right?
932 How do you know that you've made the right decisions? Have you
933 picked an interface design that will cause problems later? Have
934 you picked the most appropriate name? Do you have any questions?
936 The best way to know for sure, and pick up many helpful suggestions,
937 is to ask someone who knows. Comp.lang.perl.misc is read by just about
938 all the people who develop modules and it's the best place to ask.
940 All you need to do is post a short summary of the module, its
941 purpose and interfaces. A few lines on each of the main methods is
942 probably enough. (If you post the whole module it might be ignored
943 by busy people - generally the very people you want to read it!)
945 Don't worry about posting if you can't say when the module will be
946 ready - just say so in the message. It might be worth inviting
947 others to help you, they may be able to complete it for you!
949 =item README and other Additional Files.
951 It's well known that software developers usually fully document the
952 software they write. If, however, the world is in urgent need of
953 your software and there is not enough time to write the full
954 documentation please at least provide a README file containing:
959 A description of the module/package/extension etc.
962 A copyright notice - see below.
965 Prerequisites - what else you may need to have.
968 How to build it - possible changes to Makefile.PL etc.
974 Recent changes in this release, especially incompatibilities
977 Changes / enhancements you plan to make in the future.
981 If the README file seems to be getting too large you may wish to
982 split out some of the sections into separate files: INSTALL,
987 =item Adding a Copyright Notice.
989 How you choose to license your work is a personal decision.
990 The general mechanism is to assert your Copyright and then make
991 a declaration of how others may copy/use/modify your work.
993 Perl, for example, is supplied with two types of licence: The GNU
994 GPL and The Artistic Licence (see the files README, Copying, and
995 Artistic). Larry has good reasons for NOT just using the GNU GPL.
997 My personal recommendation, out of respect for Larry, Perl, and the
998 Perl community at large is to state something simply like:
1000 Copyright (c) 1995 Your Name. All rights reserved.
1001 This program is free software; you can redistribute it and/or
1002 modify it under the same terms as Perl itself.
1004 This statement should at least appear in the README file. You may
1005 also wish to include it in a Copying file and your source files.
1006 Remember to include the other words in addition to the Copyright.
1008 =item Give the module a version/issue/release number.
1010 To be fully compatible with the Exporter and MakeMaker modules you
1011 should store your module's version number in a non-my package
1012 variable called $VERSION. This should be a floating point
1013 number with at least two digits after the decimal (i.e., hundredths,
1014 e.g, C<$VERSION = "0.01">). Don't use a "1.3.2" style version.
1015 See Exporter.pm in Perl5.001m or later for details.
1017 It may be handy to add a function or method to retrieve the number.
1018 Use the number in announcements and archive file names when
1019 releasing the module (ModuleName-1.02.tar.Z).
1020 See perldoc ExtUtils::MakeMaker.pm for details.
1022 =item How to release and distribute a module.
1024 It's good idea to post an announcement of the availability of your
1025 module (or the module itself if small) to the comp.lang.perl.announce
1026 Usenet newsgroup. This will at least ensure very wide once-off
1029 If possible you should place the module into a major ftp archive and
1030 include details of its location in your announcement.
1032 Some notes about ftp archives: Please use a long descriptive file
1033 name that includes the version number. Most incoming directories
1034 will not be readable/listable, i.e., you won't be able to see your
1035 file after uploading it. Remember to send your email notification
1036 message as soon as possible after uploading else your file may get
1037 deleted automatically. Allow time for the file to be processed
1038 and/or check the file has been processed before announcing its
1041 FTP Archives for Perl Modules:
1043 Follow the instructions and links on
1045 http://franz.ww.tu-berlin.de/modulelist
1047 or upload to one of these sites:
1049 ftp://franz.ww.tu-berlin.de/incoming
1050 ftp://ftp.cis.ufl.edu/incoming
1052 and notify <F<upload@franz.ww.tu-berlin.de>>.
1054 By using the WWW interface you can ask the Upload Server to mirror
1055 your modules from your ftp or WWW site into your own directory on
1058 Please remember to send me an updated entry for the Module list!
1060 =item Take care when changing a released module.
1062 Always strive to remain compatible with previous released versions.
1063 Otherwise try to add a mechanism to revert to the
1064 old behaviour if people rely on it. Document incompatible changes.
1070 =head2 Guidelines for Converting Perl 4 Library Scripts into Modules
1074 =item There is no requirement to convert anything.
1076 If it ain't broke, don't fix it! Perl 4 library scripts should
1077 continue to work with no problems. You may need to make some minor
1078 changes (like escaping non-array @'s in double quoted strings) but
1079 there is no need to convert a .pl file into a Module for just that.
1081 =item Consider the implications.
1083 All Perl applications that make use of the script will need to
1084 be changed (slightly) if the script is converted into a module. Is
1085 it worth it unless you plan to make other changes at the same time?
1087 =item Make the most of the opportunity.
1089 If you are going to convert the script to a module you can use the
1090 opportunity to redesign the interface. The 'Guidelines for Module
1091 Creation' above include many of the issues you should consider.
1093 =item The pl2pm utility will get you started.
1095 This utility will read *.pl files (given as parameters) and write
1096 corresponding *.pm files. The pl2pm utilities does the following:
1101 Adds the standard Module prologue lines
1104 Converts package specifiers from ' to ::
1107 Converts die(...) to croak(...)
1110 Several other minor changes
1114 Being a mechanical process pl2pm is not bullet proof. The converted
1115 code will need careful checking, especially any package statements.
1116 Don't delete the original .pl file till the new .pm one works!
1120 =head2 Guidelines for Reusing Application Code
1124 =item Complete applications rarely belong in the Perl Module Library.
1126 =item Many applications contain some Perl code that could be reused.
1128 Help save the world! Share your code in a form that makes it easy
1131 =item Break-out the reusable code into one or more separate module files.
1133 =item Take the opportunity to reconsider and redesign the interfaces.
1135 =item In some cases the 'application' can then be reduced to a small
1137 fragment of code built on top of the reusable modules. In these cases
1138 the application could invoked as:
1140 % perl -e 'use Module::Name; method(@ARGV)' ...
1142 % perl -mModule::Name ... (in perl5.002 or higher)
1148 Perl does not enforce private and public parts of its modules as you may
1149 have been used to in other languages like C++, Ada, or Modula-17. Perl
1150 doesn't have an infatuation with enforced privacy. It would prefer
1151 that you stayed out of its living room because you weren't invited, not
1152 because it has a shotgun.
1154 The module and its user have a contract, part of which is common law,
1155 and part of which is "written". Part of the common law contract is
1156 that a module doesn't pollute any namespace it wasn't asked to. The
1157 written contract for the module (A.K.A. documentation) may make other
1158 provisions. But then you know when you C<use RedefineTheWorld> that
1159 you're redefining the world and willing to take the consequences.