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 locally 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 enable simple signal handling
88 restrict unsafe constructs
96 adopt certain VMS-specific behaviors
100 predeclare global variable names
104 =head2 Standard Modules
106 Standard, bundled modules are all expected to behave in a well-defined
107 manner with respect to namespace pollution because they use the
108 Exporter module. See their own documentation for details.
114 provide framework for multiple DBMs
118 load functions only on demand
122 split a package for autoloading
126 benchmark running times of code
130 interface to Comprehensive Perl Archive Network
132 =item CPAN::FirstTime
134 create a CPAN configuration file
138 run CPAN while avoiding compiled extensions
142 warn of errors (from perspective of caller)
146 declare struct-like datatypes
150 access Perl configuration information
154 get pathname of current working directory
158 access to Berkeley DB
160 =item Devel::SelfStubber
162 generate stubs for a SelfLoading module
166 supply object methods for directory handles
170 dynamically load C libraries into Perl code
174 use nice English (or awk) names for ugly punctuation variables
178 import environment variables
182 implements default import method for modules
184 =item ExtUtils::Embed
186 utilities for embedding Perl in C/C++ applications
188 =item ExtUtils::Install
190 install files from here to there
192 =item ExtUtils::Liblist
194 determine libraries to use and how to use them
196 =item ExtUtils::MM_OS2
198 methods to override Unix behaviour in ExtUtils::MakeMaker
200 =item ExtUtils::MM_Unix
202 methods used by ExtUtils::MakeMaker
204 =item ExtUtils::MM_VMS
206 methods to override Unix behaviour in ExtUtils::MakeMaker
208 =item ExtUtils::MakeMaker
210 create an extension Makefile
212 =item ExtUtils::Manifest
214 utilities to write and check a MANIFEST file
216 =item ExtUtils::Mkbootstrap
218 make a bootstrap file for use by DynaLoader
220 =item ExtUtils::Mksymlists
222 write linker options files for dynamic extension
224 =item ExtUtils::testlib
226 add blib/* directories to @INC
230 load the C Fcntl.h defines
234 split a pathname into pieces
236 =item File::CheckTree
238 run many filetest checks on a tree
242 compare files or filehandles
246 copy files or filehandles
254 create or remove a series of directories
258 by-name interface to Perl's builtin stat() functions
262 keep more files open than the system permits
266 supply object methods for filehandles
270 locate directory of original perl script
274 access to the gdbm library
278 extended processing of command line options
282 process single-character switches with switch clustering
286 compare 8-bit scalar data according to the current locale
290 load various IO modules
294 supply object methods for filehandles
298 supply object methods for I/O handles
302 supply object methods for pipes
306 supply seek based methods for I/O objects
310 OO interface to the select system call
314 object interface to socket communications
318 open a process for both reading and writing
322 open a process for reading, writing, and error handling
326 arbitrary length float math package
330 arbitrary size integer math package
334 complex numbers and associated mathematical functions
338 simple interface to parts of Math::Complex for those who
339 need trigonometric functions only for real numbers
343 tied access to ndbm files
351 by-name interface to Perl's builtin gethost*() functions
355 by-name interface to Perl's builtin getnet*() functions
359 by-name interface to Perl's builtin getproto*() functions
363 by-name interface to Perl's builtin getserv*() functions
367 disable named opcodes when compiling or running perl code
371 convert POD data to formatted ASCII text
375 interface to IEEE Standard 1003.1
379 tied access to sdbm files
383 compile and execute code in restricted compartments
387 search for key in dictionary file
391 save and restore selected file handle
395 load functions only on demand
399 run shell commands transparently within perl
403 load the C socket.h defines and structure manipulators
407 manipulate Perl symbols and their names
411 try every conceivable way to get hostname
415 interface to the Unix syslog(3) calls
423 word completion module
427 interface to various C<readline> packages
431 run perl standard test scripts with statistics
435 create an abbreviation table from a list
437 =item Text::ParseWords
439 parse text into an array of tokens
443 implementation of the Soundex Algorithm as described by Knuth
447 expand and unexpand tabs per the Unix expand(1) and unexpand(1)
451 line wrapping to form simple paragraphs
455 base class definitions for tied hashes
459 base class definitions for tied hashes with references as keys
463 base class definitions for tied scalars
465 =item Tie::SubstrHash
467 fixed-table-size, fixed-key-length hashing
471 efficiently compute time from local and GMT time
475 by-name interface to Perl's builtin gmtime() function
477 =item Time::localtime
479 by-name interface to Perl's builtin localtime() function
483 internal object used by Time::gmtime and Time::localtime
487 base class for ALL classes (blessed references)
491 by-name interface to Perl's builtin getgr*() functions
495 by-name interface to Perl's builtin getpw*() functions
499 To find out I<all> the modules installed on your system, including
500 those without documentation or outside the standard release, do this:
502 find `perl -e 'print "@INC"'` -name '*.pm' -print
504 They should all have their own documentation installed and accessible via
505 your system man(1) command. If that fails, try the I<perldoc> program.
507 =head2 Extension Modules
509 Extension modules are written in C (or a mix of Perl and C) and may be
510 statically linked or in general are
511 dynamically loaded into Perl if and when you need them. Supported
512 extension modules include the Socket, Fcntl, and POSIX modules.
514 Many popular C extension modules do not come bundled (at least, not
515 completely) due to their sizes, volatility, or simply lack of time for
516 adequate testing and configuration across the multitude of platforms on
517 which Perl was beta-tested. You are encouraged to look for them in
518 archie(1L), the Perl FAQ or Meta-FAQ, the WWW page, and even with their
519 authors before randomly posting asking for their present condition and
524 CPAN stands for the Comprehensive Perl Archive Network. This is a globally
525 replicated collection of all known Perl materials, including hundreds
526 of unbundled modules. Here are the major categories of modules:
531 Language Extensions and Documentation Tools
537 Operating System Interfaces
540 Networking, Device Control (modems) and InterProcess Communication
543 Data Types and Data Type Utilities
552 Interfaces to / Emulations of Other Programming Languages
555 File Names, File Systems and File Locking (see also File Handles)
558 String Processing, Language Text Processing, Parsing, and Searching
561 Option, Argument, Parameter, and Configuration File Processing
564 Internationalization and Locale
567 Authentication, Security, and Encryption
570 World Wide Web, HTML, HTTP, CGI, MIME
573 Server and Daemon Utilities
576 Archiving and Compression
579 Images, Pixmap and Bitmap Manipulation, Drawing, and Graphing
585 Control Flow Utilities (callbacks and exceptions etc)
588 File Handle and Input/Output Stream Utilities
591 Miscellaneous Modules
595 The registered CPAN sites as of this writing include the following.
596 You should try to choose one close to you:
603 South Africa ftp://ftp.is.co.za/programming/perl/CPAN/
608 Hong Kong ftp://ftp.hkstar.com/pub/CPAN/
609 Japan ftp://ftp.jaist.ac.jp/pub/lang/perl/CPAN/
610 ftp://ftp.lab.kdd.co.jp/lang/perl/CPAN/
611 South Korea ftp://ftp.nuri.net/pub/CPAN/
612 Taiwan ftp://dongpo.math.ncu.edu.tw/perl/CPAN/
613 ftp://ftp.wownet.net/pub2/PERL/
618 Australia ftp://ftp.netinfo.com.au/pub/perl/CPAN/
619 New Zealand ftp://ftp.tekotago.ac.nz/pub/perl/CPAN/
624 Austria ftp://ftp.tuwien.ac.at/pub/languages/perl/CPAN/
625 Belgium ftp://ftp.kulnet.kuleuven.ac.be/pub/mirror/CPAN/
626 Czech Republic ftp://sunsite.mff.cuni.cz/Languages/Perl/CPAN/
627 Denmark ftp://sunsite.auc.dk/pub/languages/perl/CPAN/
628 Finland ftp://ftp.funet.fi/pub/languages/perl/CPAN/
629 France ftp://ftp.ibp.fr/pub/perl/CPAN/
630 ftp://ftp.pasteur.fr/pub/computing/unix/perl/CPAN/
631 Germany ftp://ftp.gmd.de/packages/CPAN/
632 ftp://ftp.leo.org/pub/comp/programming/languages/perl/CPAN/
633 ftp://ftp.mpi-sb.mpg.de/pub/perl/CPAN/
634 ftp://ftp.rz.ruhr-uni-bochum.de/pub/CPAN/
635 ftp://ftp.uni-erlangen.de/pub/source/Perl/CPAN/
636 ftp://ftp.uni-hamburg.de/pub/soft/lang/perl/CPAN/
637 Greece ftp://ftp.ntua.gr/pub/lang/perl/
638 Hungary ftp://ftp.kfki.hu/pub/packages/perl/CPAN/
639 Italy ftp://cis.utovrm.it/CPAN/
640 the Netherlands ftp://ftp.cs.ruu.nl/pub/PERL/CPAN/
641 ftp://ftp.EU.net/packages/cpan/
642 Norway ftp://ftp.uit.no/pub/languages/perl/cpan/
643 Poland ftp://ftp.pk.edu.pl/pub/lang/perl/CPAN/
644 ftp://sunsite.icm.edu.pl/pub/CPAN/
645 Portugal ftp://ftp.ci.uminho.pt/pub/lang/perl/
646 ftp://ftp.telepac.pt/pub/CPAN/
647 Russia ftp://ftp.sai.msu.su/pub/lang/perl/CPAN/
648 Slovenia ftp://ftp.arnes.si/software/perl/CPAN/
649 Spain ftp://ftp.etse.urv.es/pub/mirror/perl/
650 ftp://ftp.rediris.es/mirror/CPAN/
651 Sweden ftp://ftp.sunet.se/pub/lang/perl/CPAN/
652 UK ftp://ftp.demon.co.uk/pub/mirrors/perl/CPAN/
653 ftp://sunsite.doc.ic.ac.uk/packages/CPAN/
654 ftp://unix.hensa.ac.uk/mirrors/perl-CPAN/
659 Ontario ftp://ftp.utilis.com/public/CPAN/
660 ftp://enterprise.ic.gc.ca/pub/perl/CPAN/
661 Manitoba ftp://theory.uwinnipeg.ca/pub/CPAN/
662 California ftp://ftp.digital.com/pub/plan/perl/CPAN/
663 ftp://ftp.cdrom.com/pub/perl/CPAN/
664 Colorado ftp://ftp.cs.colorado.edu/pub/perl/CPAN/
665 Florida ftp://ftp.cis.ufl.edu/pub/perl/CPAN/
666 Illinois ftp://uiarchive.uiuc.edu/pub/lang/perl/CPAN/
667 Massachusetts ftp://ftp.iguide.com/pub/mirrors/packages/perl/CPAN/
668 New York ftp://ftp.rge.com/pub/languages/perl/
669 North Carolina ftp://ftp.duke.edu/pub/perl/
670 Oklahoma ftp://ftp.ou.edu/mirrors/CPAN/
671 Oregon http://www.perl.org/CPAN/
672 ftp://ftp.orst.edu/pub/packages/CPAN/
673 Pennsylvania ftp://ftp.epix.net/pub/languages/perl/
674 Texas ftp://ftp.sedl.org/pub/mirrors/CPAN/
675 ftp://ftp.metronet.com/pub/perl/
680 Chile ftp://sunsite.dcc.uchile.cl/pub/Lang/perl/CPAN/
684 For an up-to-date listing of CPAN sites,
685 see F<http://www.perl.com/perl/CPAN> or F<ftp://ftp.perl.com/perl/>.
687 =head1 Modules: Creation, Use, and Abuse
689 (The following section is borrowed directly from Tim Bunce's modules
690 file, available at your nearest CPAN site.)
692 Perl implements a class using a package, but the presence of a
693 package doesn't imply the presence of a class. A package is just a
694 namespace. A class is a package that provides subroutines that can be
695 used as methods. A method is just a subroutine that expects, as its
696 first argument, either the name of a package (for "static" methods),
697 or a reference to something (for "virtual" methods).
699 A module is a file that (by convention) provides a class of the same
700 name (sans the .pm), plus an import method in that class that can be
701 called to fetch exported symbols. This module may implement some of
702 its methods by loading dynamic C or C++ objects, but that should be
703 totally transparent to the user of the module. Likewise, the module
704 might set up an AUTOLOAD function to slurp in subroutine definitions on
705 demand, but this is also transparent. Only the F<.pm> file is required to
706 exist. See L<perlsub>, L<perltoot>, and L<AutoLoader> for details about
707 the AUTOLOAD mechanism.
709 =head2 Guidelines for Module Creation
713 =item Do similar modules already exist in some form?
715 If so, please try to reuse the existing modules either in whole or
716 by inheriting useful features into a new class. If this is not
717 practical try to get together with the module authors to work on
718 extending or enhancing the functionality of the existing modules.
719 A perfect example is the plethora of packages in perl4 for dealing
720 with command line options.
722 If you are writing a module to expand an already existing set of
723 modules, please coordinate with the author of the package. It
724 helps if you follow the same naming scheme and module interaction
725 scheme as the original author.
727 =item Try to design the new module to be easy to extend and reuse.
729 Use blessed references. Use the two argument form of bless to bless
730 into the class name given as the first parameter of the constructor,
735 return bless {}, $class;
738 or even this if you'd like it to be used as either a static
743 my $class = ref($self) || $self;
744 return bless {}, $class;
747 Pass arrays as references so more parameters can be added later
748 (it's also faster). Convert functions into methods where
749 appropriate. Split large methods into smaller more flexible ones.
750 Inherit methods from other modules if appropriate.
752 Avoid class name tests like: C<die "Invalid" unless ref $ref eq 'FOO'>.
753 Generally you can delete the "C<eq 'FOO'>" part with no harm at all.
754 Let the objects look after themselves! Generally, avoid hard-wired
755 class names as far as possible.
757 Avoid C<$r-E<gt>Class::func()> where using C<@ISA=qw(... Class ...)> and
758 C<$r-E<gt>func()> would work (see L<perlbot> for more details).
760 Use autosplit so little used or newly added functions won't be a
761 burden to programs which don't use them. Add test functions to
762 the module after __END__ either using AutoSplit or by saying:
764 eval join('',<main::DATA>) || die $@ unless caller();
766 Does your module pass the 'empty subclass' test? If you say
767 "C<@SUBCLASS::ISA = qw(YOURCLASS);>" your applications should be able
768 to use SUBCLASS in exactly the same way as YOURCLASS. For example,
769 does your application still work if you change: C<$obj = new YOURCLASS;>
770 into: C<$obj = new SUBCLASS;> ?
772 Avoid keeping any state information in your packages. It makes it
773 difficult for multiple other packages to use yours. Keep state
774 information in objects.
776 Always use B<-w>. Try to C<use strict;> (or C<use strict qw(...);>).
777 Remember that you can add C<no strict qw(...);> to individual blocks
778 of code which need less strictness. Always use B<-w>. Always use B<-w>!
779 Follow the guidelines in the perlstyle(1) manual.
781 =item Some simple style guidelines
783 The perlstyle manual supplied with perl has many helpful points.
785 Coding style is a matter of personal taste. Many people evolve their
786 style over several years as they learn what helps them write and
787 maintain good code. Here's one set of assorted suggestions that
788 seem to be widely used by experienced developers:
790 Use underscores to separate words. It is generally easier to read
791 $var_names_like_this than $VarNamesLikeThis, especially for
792 non-native speakers of English. It's also a simple rule that works
793 consistently with VAR_NAMES_LIKE_THIS.
795 Package/Module names are an exception to this rule. Perl informally
796 reserves lowercase module names for 'pragma' modules like integer
797 and strict. Other modules normally begin with a capital letter and
798 use mixed case with no underscores (need to be short and portable).
800 You may find it helpful to use letter case to indicate the scope
801 or nature of a variable. For example:
803 $ALL_CAPS_HERE constants only (beware clashes with perl vars)
804 $Some_Caps_Here package-wide global/static
805 $no_caps_here function scope my() or local() variables
807 Function and method names seem to work best as all lowercase.
808 e.g., C<$obj-E<gt>as_string()>.
810 You can use a leading underscore to indicate that a variable or
811 function should not be used outside the package that defined it.
813 =item Select what to export.
815 Do NOT export method names!
817 Do NOT export anything else by default without a good reason!
819 Exports pollute the namespace of the module user. If you must
820 export try to use @EXPORT_OK in preference to @EXPORT and avoid
821 short or common names to reduce the risk of name clashes.
823 Generally anything not exported is still accessible from outside the
824 module using the ModuleName::item_name (or C<$blessed_ref-E<gt>method>)
825 syntax. By convention you can use a leading underscore on names to
826 indicate informally that they are 'internal' and not for public use.
828 (It is actually possible to get private functions by saying:
829 C<my $subref = sub { ... }; &$subref;>. But there's no way to call that
830 directly as a method, because a method must have a name in the symbol
833 As a general rule, if the module is trying to be object oriented
834 then export nothing. If it's just a collection of functions then
835 @EXPORT_OK anything but use @EXPORT with caution.
837 =item Select a name for the module.
839 This name should be as descriptive, accurate, and complete as
840 possible. Avoid any risk of ambiguity. Always try to use two or
841 more whole words. Generally the name should reflect what is special
842 about what the module does rather than how it does it. Please use
843 nested module names to group informally or categorize a module.
844 There should be a very good reason for a module not to have a nested name.
845 Module names should begin with a capital letter.
847 Having 57 modules all called Sort will not make life easy for anyone
848 (though having 23 called Sort::Quick is only marginally better :-).
849 Imagine someone trying to install your module alongside many others.
850 If in any doubt ask for suggestions in comp.lang.perl.misc.
852 If you are developing a suite of related modules/classes it's good
853 practice to use nested classes with a common prefix as this will
854 avoid namespace clashes. For example: Xyz::Control, Xyz::View,
855 Xyz::Model etc. Use the modules in this list as a naming guide.
857 If adding a new module to a set, follow the original author's
858 standards for naming modules and the interface to methods in
861 To be portable each component of a module name should be limited to
862 11 characters. If it might be used on MS-DOS then try to ensure each is
863 unique in the first 8 characters. Nested modules make this easier.
865 =item Have you got it right?
867 How do you know that you've made the right decisions? Have you
868 picked an interface design that will cause problems later? Have
869 you picked the most appropriate name? Do you have any questions?
871 The best way to know for sure, and pick up many helpful suggestions,
872 is to ask someone who knows. Comp.lang.perl.misc is read by just about
873 all the people who develop modules and it's the best place to ask.
875 All you need to do is post a short summary of the module, its
876 purpose and interfaces. A few lines on each of the main methods is
877 probably enough. (If you post the whole module it might be ignored
878 by busy people - generally the very people you want to read it!)
880 Don't worry about posting if you can't say when the module will be
881 ready - just say so in the message. It might be worth inviting
882 others to help you, they may be able to complete it for you!
884 =item README and other Additional Files.
886 It's well known that software developers usually fully document the
887 software they write. If, however, the world is in urgent need of
888 your software and there is not enough time to write the full
889 documentation please at least provide a README file containing:
894 A description of the module/package/extension etc.
897 A copyright notice - see below.
900 Prerequisites - what else you may need to have.
903 How to build it - possible changes to Makefile.PL etc.
909 Recent changes in this release, especially incompatibilities
912 Changes / enhancements you plan to make in the future.
916 If the README file seems to be getting too large you may wish to
917 split out some of the sections into separate files: INSTALL,
922 =item Adding a Copyright Notice.
924 How you choose to license your work is a personal decision.
925 The general mechanism is to assert your Copyright and then make
926 a declaration of how others may copy/use/modify your work.
928 Perl, for example, is supplied with two types of licence: The GNU
929 GPL and The Artistic Licence (see the files README, Copying, and
930 Artistic). Larry has good reasons for NOT just using the GNU GPL.
932 My personal recommendation, out of respect for Larry, Perl, and the
933 perl community at large is to state something simply like:
935 Copyright (c) 1995 Your Name. All rights reserved.
936 This program is free software; you can redistribute it and/or
937 modify it under the same terms as Perl itself.
939 This statement should at least appear in the README file. You may
940 also wish to include it in a Copying file and your source files.
941 Remember to include the other words in addition to the Copyright.
943 =item Give the module a version/issue/release number.
945 To be fully compatible with the Exporter and MakeMaker modules you
946 should store your module's version number in a non-my package
947 variable called $VERSION. This should be a floating point
948 number with at least two digits after the decimal (i.e., hundredths,
949 e.g, C<$VERSION = "0.01">). Don't use a "1.3.2" style version.
950 See Exporter.pm in Perl5.001m or later for details.
952 It may be handy to add a function or method to retrieve the number.
953 Use the number in announcements and archive file names when
954 releasing the module (ModuleName-1.02.tar.Z).
955 See perldoc ExtUtils::MakeMaker.pm for details.
957 =item How to release and distribute a module.
959 It's good idea to post an announcement of the availability of your
960 module (or the module itself if small) to the comp.lang.perl.announce
961 Usenet newsgroup. This will at least ensure very wide once-off
964 If possible you should place the module into a major ftp archive and
965 include details of its location in your announcement.
967 Some notes about ftp archives: Please use a long descriptive file
968 name which includes the version number. Most incoming directories
969 will not be readable/listable, i.e., you won't be able to see your
970 file after uploading it. Remember to send your email notification
971 message as soon as possible after uploading else your file may get
972 deleted automatically. Allow time for the file to be processed
973 and/or check the file has been processed before announcing its
976 FTP Archives for Perl Modules:
978 Follow the instructions and links on
980 http://franz.ww.tu-berlin.de/modulelist
982 or upload to one of these sites:
984 ftp://franz.ww.tu-berlin.de/incoming
985 ftp://ftp.cis.ufl.edu/incoming
987 and notify <F<upload@franz.ww.tu-berlin.de>>.
989 By using the WWW interface you can ask the Upload Server to mirror
990 your modules from your ftp or WWW site into your own directory on
993 Please remember to send me an updated entry for the Module list!
995 =item Take care when changing a released module.
997 Always strive to remain compatible with previous released versions
998 (see 2.2 above) Otherwise try to add a mechanism to revert to the
999 old behaviour if people rely on it. Document incompatible changes.
1005 =head2 Guidelines for Converting Perl 4 Library Scripts into Modules
1009 =item There is no requirement to convert anything.
1011 If it ain't broke, don't fix it! Perl 4 library scripts should
1012 continue to work with no problems. You may need to make some minor
1013 changes (like escaping non-array @'s in double quoted strings) but
1014 there is no need to convert a .pl file into a Module for just that.
1016 =item Consider the implications.
1018 All the perl applications which make use of the script will need to
1019 be changed (slightly) if the script is converted into a module. Is
1020 it worth it unless you plan to make other changes at the same time?
1022 =item Make the most of the opportunity.
1024 If you are going to convert the script to a module you can use the
1025 opportunity to redesign the interface. The 'Guidelines for Module
1026 Creation' above include many of the issues you should consider.
1028 =item The pl2pm utility will get you started.
1030 This utility will read *.pl files (given as parameters) and write
1031 corresponding *.pm files. The pl2pm utilities does the following:
1036 Adds the standard Module prologue lines
1039 Converts package specifiers from ' to ::
1042 Converts die(...) to croak(...)
1045 Several other minor changes
1049 Being a mechanical process pl2pm is not bullet proof. The converted
1050 code will need careful checking, especially any package statements.
1051 Don't delete the original .pl file till the new .pm one works!
1055 =head2 Guidelines for Reusing Application Code
1059 =item Complete applications rarely belong in the Perl Module Library.
1061 =item Many applications contain some perl code which could be reused.
1063 Help save the world! Share your code in a form that makes it easy
1066 =item Break-out the reusable code into one or more separate module files.
1068 =item Take the opportunity to reconsider and redesign the interfaces.
1070 =item In some cases the 'application' can then be reduced to a small
1072 fragment of code built on top of the reusable modules. In these cases
1073 the application could invoked as:
1075 perl -e 'use Module::Name; method(@ARGV)' ...
1077 perl -mModule::Name ... (in perl5.002 or higher)
1083 Perl does not enforce private and public parts of its modules as you may
1084 have been used to in other languages like C++, Ada, or Modula-17. Perl
1085 doesn't have an infatuation with enforced privacy. It would prefer
1086 that you stayed out of its living room because you weren't invited, not
1087 because it has a shotgun.
1089 The module and its user have a contract, part of which is common law,
1090 and part of which is "written". Part of the common law contract is
1091 that a module doesn't pollute any namespace it wasn't asked to. The
1092 written contract for the module (A.K.A. documentation) may make other
1093 provisions. But then you know when you C<use RedefineTheWorld> that
1094 you're redefining the world and willing to take the consequences.