Inline - Write Perl subroutines in other programming languages.
use Inline C;
print "9 + 16 = ", add(9, 16), "\n";
print "9 - 16 = ", subtract(9, 16), "\n";
__END__
__C__
int add(int x, int y) {
return x + y;
}
int subtract(int x, int y) {
return x - y;
}
The Inline module allows you to put source code from other programming languages directly "inline" in a Perl script or module. The code is automatically compiled as needed, and then loaded for immediate access from Perl.
Inline saves you from the hassle of having to write and compile your own glue code using facilities like XS or SWIG. Simply type the code where you want it and run your Perl as normal. All the hairy details are handled for you. The compilation and installation of your code chunks all happen transparently; all you will notice is the delay of compilation on the first run.
The Inline code only gets compiled the first time you run it (or whenever it is modified) so you only take the performance hit once. Code that is Inlined into distributed modules (like on the CPAN) will get compiled when the module is installed, so the end user will never notice the compilation time.
Best of all, it works the same on both Unix and Microsoft Windows. See Inline-Support for support information.
Do you want to know "Why would I use other languages in Perl?" or "Why should I use Inline to do it?"? I'll try to answer both.
The most obvious reason is performance. For an interpreted language, Perl is very fast. Many people will say "Anything Perl can do, C can do faster". (They never mention the development time :-) Anyway, you may be able to remove a bottleneck in your Perl code by using another language, without having to write the entire program in that language. This keeps your overall development time down, because you're using Perl for all of the non-critical code.
Another reason is to access functionality from existing API-s that use the language. Some of this code may only be available in binary form. But by creating small subroutines in the native language, you can "glue" existing libraries to your Perl. As a user of the CPAN, you know that code reuse is a good thing. So why throw away those Fortran libraries just yet?
If you are using Inline with the C language, then you can access the full internals of Perl itself. This opens up the floodgates to both extreme power and peril.
Maybe the best reason is "Because you want to!". Diversity keeps the world interesting. TMTOWTDI!
There are already two major facilities for extending Perl with C. They are XS and SWIG. Both are similar in their capabilities, at least as far as Perl is concerned. And both of them are quite difficult to learn compared to Inline.
There is a big fat learning curve involved with setting up and using the XS environment. You need to get quite intimate with the following docs:
* perlxs * perlxstut * perlapi * perlguts * perlmod * h2xs * xsubpp * ExtUtils::MakeMaker
With Inline you can be up and running in minutes. There is a C Cookbook with lots of short but complete programs that you can extend to your real-life problems. No need to learn about the complicated build process going on in the background. You don't even need to compile the code yourself. Inline takes care of every last detail except writing the C code.
Perl programmers cannot be bothered with silly things like compiling. "Tweak, Run, Tweak, Run" is our way of life. Inline does all the dirty work for you.
Another advantage of Inline is that you can use it directly in a script. You can even use it in a Perl one-liner. With XS and SWIG, you always set up an entirely separate module. Even if you only have one or two functions. Inline makes easy things easy, and hard things possible. Just like Perl.
Finally, Inline supports several programming languages (not just C and C++). As of this writing, Inline has support for C, C++, Java, Python, Ruby, Tcl, Assembler, Basic, Guile, Befunge, Octave, Awk, BC, TT (Template Toolkit), WebChat and even PERL. New Inline Language Support Modules (ILSMs) are regularly being added. See Inline-API for details on how to create your own ILSM.
Inline is a little bit different than most of the Perl modules that you
are used to. It doesn't import any functions into your namespace and it
doesn't have any object oriented methods. Its entire interface (with two
minor exceptions) is specified through the 'use Inline ...' command.
This section will explain all of the different ways to use Inline. If
you want to begin using C with Inline immediately, see
Inline::C-Cookbook.
The most basic form for using Inline is:
use Inline X => "X source code";
where 'X' is one of the supported Inline programming languages. The second parameter identifies the source code that you want to bind to Perl. The source code can be specified using any of the following syntaxes:
use Inline Java => 'DATA';
# Perl code goes here ...
__DATA__
__Java__
/* Java code goes here ... */
The easiest and most visually clean way to specify your source code in
an Inline Perl program is to use the special DATA keyword. This tells
Inline to look for a special marker in your DATA filehandle's input
stream. In this example the special marker is __Java__, which is the
programming language surrounded by double underscores.
In case you've forgotten, the DATA pseudo file is comprised of all
the text after the __END__ or __DATA__ section of your program. If
you're working outside the main package, you'd best use the
__DATA__ marker or else Inline will not find your code.
Using this scheme keeps your Perl code at the top, and all the ugly Java stuff down below where it belongs. This is visually clean and makes for more maintainable code. An excellent side benefit is that you don't have to escape any characters like you might in a Perl string. The source code is verbatim. For these reasons, I prefer this method the most.
The only problem with this style is that since Perl can't read the
DATA filehandle until runtime, it obviously can't bind your functions
until runtime. The net effect of this is that you can't use your Inline
functions as barewords (without predeclaring them) because Perl has no
idea they exist during compile time.
use Inline::Files;
use Inline Java => 'FILE';
# Perl code goes here ...
__JAVA__
/* Java code goes here ... */
This is the newest method of specifying your source code. It makes use
of the Perl module Inline::Files written by Damian Conway. The basic
style and meaning are the same as for the DATA keyword, but there are
a few syntactic and semantic twists.
First, you must say 'use Inline::Files' before you 'use Inline' code
that needs those files. The special 'DATA' keyword is replaced by
either 'FILE' or 'BELOW'. This allows for the bad pun idiom of:
use Inline C => 'BELOW';
You can omit the __DATA__ tag now. Inline::Files is a source filter
that will remove these sections from your program before Perl compiles
it. They are then available for Inline to make use of. And since this
can all be done at compile time, you don't have to worry about the
caveats of the 'DATA' keyword.
This module has a couple small gotchas. Since Inline::Files only recognizes file markers with capital letters, you must specify the capital form of your language name. Also, there is a startup time penalty for using a source code filter.
At this point Inline::Files is alpha software and use of it is experimental. Inline's integration of this module is also fledgling at the time being. One of things I plan to do with Inline::Files is to get line number info so when an extension doesn't compile, the error messages will point to the correct source file and line number.
My best advice is to use Inline::Files for testing (especially as support for it improves), but use DATA for production and distributed/CPAN code.
use Inline Java => <<'END';
/* Java code goes here ... */
END
# Perl code goes here ...
You also just specify the source code as a single string. A handy way to write the string is to use Perl's "here document" style of quoting. This is ok for small functions but can get unwieldy in the large. On the other hand, the string variant probably has the least startup penalty and all functions are bound at compile time.
If you wish to put the string into a scalar variable, please be aware
that the use statement is a compile time directive. As such, all the
variables it uses must also be set at compile time, before the 'use
Inline' statement. Here is one way to do it:
my $code;
BEGIN {
$code = <<END;
/* Java code goes here ... */
END
}
use Inline Java => $code;
# Perl code goes here ...
An alternative to using the BEGIN block method is to specify the source
code at run time using the 'Inline->bind()' method. (This is one of the
interface exceptions mentioned above) The bind() method takes the
same arguments as 'use Inline ...'.
my $code = <<END;
/* Java code goes here ... */
END
Inline->bind(Java => $code);
You can think of bind() as a way to eval() code in other
programming languages.
Although bind() is a powerful feature, it is not recommended for use in Inline based modules. In fact, it won't work at all for installable modules. See instructions below for creating modules with Inline.
If you are using the 'DATA' or 'FILE' methods described above and there are no extra parameters, you can omit the keyword altogether. For example:
use Inline 'Java';
# Perl code goes here ...
__DATA__
__Java__
/* Java code goes here ... */
or
use Inline::Files;
use Inline 'Java';
# Perl code goes here ...
__JAVA__
/* Java code goes here ... */
If you are writing a module, you can also use the DATA section for POD
and AutoLoader subroutines. Just be sure to put them before the first
Inline marker. If you install the helper module Inline::Filters, you
can even use POD inside your Inline code. You just have to specify a
filter to strip it out.
You can also specify multiple Inline sections, possibly in different programming languages. Here is another example:
# The module Foo.pm
package Foo;
use AutoLoader;
use Inline C;
use Inline C => DATA => FILTERS => 'Strip_POD';
use Inline Python;
1;
__DATA__
sub marine {
# This is an autoloaded subroutine
}
=head1 External subroutines
=cut
__C__
/* First C section */
__C__
/* Second C section */
=head1 My C Function
Some POD doc.
=cut
__Python__
"""A Python Section"""
An important thing to remember is that you need to have one "use Inline Foo => 'DATA'" for each "__Foo__" marker, and they must be in the same order. This allows you to apply different configuration options to each section.
Inline trys to do the right thing as often as possible. But sometimes you may need to override the default actions. This is easy to do. Simply list the Inline configuration options after the regular Inline parameters. All congiguration options are specified as (key, value) pairs.
use Inline (C => 'DATA',
DIRECTORY => './inline_dir',
LIBS => '-lfoo',
INC => '-I/foo/include',
PREFIX => 'XXX_',
WARNINGS => 0,
);
You can also specify the configuration options on a separate Inline call like this:
use Inline (C => Config =>
DIRECTORY => './inline_dir',
LIBS => '-lfoo',
INC => '-I/foo/include',
PREFIX => 'XXX_',
WARNINGS => 0,
);
use Inline C => <<'END_OF_C_CODE';
The special keyword 'Config' tells Inline that this is a
configuration-only call. No source code will be compiled or bound to
Perl.
If you want to specify global configuration options that don't apply to a particular language, just leave the language out of the call. Like this:
use Inline Config => WARNINGS => 0;
The Config options are inherited and additive. You can use as many Config calls as you want. And you can apply different options to different code sections. When a source code section is passed in, Inline will apply whichever options have been specified up to that point. Here is a complex configuration example:
use Inline (Config =>
DIRECTORY => './inline_dir',
);
use Inline (C => Config =>
LIBS => '-lglobal',
);
use Inline (C => 'DATA', # First C Section
LIBS => ['-llocal1', '-llocal2'],
);
use Inline (Config =>
WARNINGS => 0,
);
use Inline (Python => 'DATA', # First Python Section
LIBS => '-lmypython1',
);
use Inline (C => 'DATA', # Second C Section
LIBS => [undef, '-llocal3'],
);
The first Config applies to all subsequent calls. The second
Config applies to all subsequent C sections (but not Python
sections). In the first C section, the external libraries global,
local1 and local2 are used. (Most options allow either string or
array ref forms, and do the right thing.) The Python section does not
use the global library, but does use the same DIRECTORY, and has
warnings turned off. The second C section only uses the local3
library. That's because a value of undef resets the additive
behavior.
The DIRECTORY and WARNINGS options are generic Inline options. All
other options are language specific. To find out what the C options
do, see Inline::C.
If a particular config option has value options of 1 and 0, you can use the ENABLE and DISABLE modifiers. In other words, this:
use Inline Config =>
FORCE_BUILD => 1,
CLEAN_AFTER_BUILD => 0;
could be reworded as:
use Inline Config =>
ENABLE => FORCE_BUILD,
DISABLE => CLEAN_AFTER_BUILD;
Inline has a special configuration syntax that tells it to get more configuration options from other Perl modules. Here is an example:
use Inline with => 'Event';
This tells Inline to load the module Event.pm and ask it for
configuration information. Since Event has a C API of its own, it can
pass Inline all of the information it needs to be able to use Event C
callbacks seamlessly.
That means that you don't need to specify the typemaps, shared libraries, include files and other information required to get this to work.
You can specify a single module or a list of them. Like:
use Inline with => qw(Event Foo Bar);
Currently, Event is the only module that works with Inline.
Inline lets you set many configuration options from the command line. These options are called 'shortcuts'. They can be very handy, especially when you only want to set the options temporarily, for say, debugging.
For instance, to get some general information about your Inline code in
the script Foo.pl, use the command:
perl -MInline=INFO Foo.pl
If you want to force your code to compile, even if its already done, use:
perl -MInline=FORCE Foo.pl
If you want to do both, use:
perl -MInline=INFO -MInline=FORCE Foo.pl
or better yet:
perl -MInline=INFO,FORCE Foo.pl
Inline needs a place to build your code and to install the results of
the build. It uses a single directory named '.Inline/' under normal
circumstances. If you create this directory in your home directory, the
current directory or in the directory where your program resides, Inline
will find and use it. You can also specify it in the environment
variable PERL_INLINE_DIRECTORY or directly in your program, by using
the DIRECTORY keyword option. If Inline cannot find the directory in
any of these places it will create a '_Inline/' directory in either
your current directory or the directory where your script resides.
One of the key factors to using Inline successfully, is understanding
this directory. When developing code it is usually best to create this
directory (or let Inline do it) in your current directory. Remember that
there is nothing sacred about this directory except that it holds your
compiled code. Feel free to delete it at any time. Inline will simply
start from scratch and recompile your code on the next run. If you have
several programs that you want to force to recompile, just delete your
'.Inline/' directory.
It is probably best to have a separate '.Inline/' directory for each
project that you are working on. You may want to keep stable code in the
<.Inline/> in your home directory. On multi-user systems, each user
should have their own '.Inline/' directories. It could be a security
risk to put the directory in a shared place like /tmp/.
All programmers make mistakes. When you make a mistake with Inline, like writing bad C code, you'll get a big error report on your screen. This report tells you where to look to do the debugging. Some languages may also dump out the error messages generated from the build.
When Inline needs to build something it creates a subdirectory under
your DIRECTORY/build/ directory. This is where it writes all the
components it needs to build your extension. Things like XS files,
Makefiles and output log files.
If everything goes OK, Inline will delete this subdirectory. If there is an error, Inline will leave the directory intact and print its location. The idea is that you are supposed to go into that directory and figure out what happened.
Read the doc for your particular Inline Language Support Module for more information.
Inline keeps a cached file of all of the Inline Language Support
Module's meta data in a file called config. This file can be found in
your DIRECTORY directory. If the file does not exist, Inline creates
a new one. It will search your system for any module beginning with
Inline::. It will then call that module's register() method to get
useful information for future invocations.
Whenever you add a new ILSM, you should delete this file so that Inline will auto-discover your newly installed language module.
This section lists all of the generic Inline configuration options. For language specific configuration, see the doc for that language.
The DIRECTORY config option is the directory that Inline uses to both
build and install an extension.
Normally Inline will search in a bunch of known places for a directory
called '.Inline/'. Failing that, it will create a directory called
'_Inline/'
If you want to specify your own directory, use this configuration option.
Note that you must create the DIRECTORY directory yourself. Inline
will not do it for you.
You can use this option to set the name of your Inline extension object module. For example:
use Inline C => 'DATA',
NAME => 'Foo::Bar';
would cause your C code to be compiled in to the object:
lib/auto/Foo/Bar/Bar.so
lib/auto/Foo/Bar/Bar.inl
(The .inl component contains dependency information to make sure the source code is in sync with the executable)
If you don't use NAME, Inline will pick a name for you based on your program name or package name. In this case, Inline will also enable the AUTONAME option which mangles in a small piece of the MD5 fingerprint into your object name, to make it unique.
This option is enabled whenever the NAME parameter is not specified. To disable it say:
use Inline C => 'DATA',
DISABLE => 'AUTONAME';
AUTONAME mangles in enough of the MD5 fingerprint to make your module name unique. Objects created with AUTONAME will never get replaced. That also means they will never get cleaned up automatically.
AUTONAME is very useful for small throw away scripts. For more serious things, always use the NAME option.
Specifies the version number of the Inline extension object. It is used only for modules, and it must match the global variable $VERSION. Additionally, this option should used if (and only if) a module is being set up to be installed permanently into the Perl sitelib tree. Inline will croak if you use it otherwise.
The presence of the VERSION parameter is the official way to let Inline know that your code is an installable/installed module. Inline will never generate an object in the temporary cache (_Inline/ directory) if VERSION is set. It will also never try to recompile a module that was installed into someone's Perl site tree.
So the basic rule is develop without VERSION, and deliver with VERSION.
WITH can also be used as a configuration option instead of using the
special 'with' syntax. Do this if you want to use different sections of
Inline code with different modules. (Probably a very rare usage)
use Event;
use Inline C => DATA => WITH => 'Event';
Modules specified using the config form of WITH will not be
automatically required. You must use them yourself.
This option is for compiled languages only. It tells Inline to tell
DynaLoader to load an object file in such a way that its symbols can be
dynamically resolved by other object files. May not work on all
platforms. See the GLOBAL shortcut below.
You must use this option whenever you use Perl's -T switch, for taint
checking. This option tells Inline to blindly untaint all tainted
variables. It also turns on SAFEMODE by default. See the UNTAINT
shortcut below.
Perform extra safety checking, in an attempt to thwart malicious code. This option cannot guarantee security, but it does turn on all the currently implemented checks.
There is a slight startup penalty by using SAFEMODE. Also, using UNTAINT
automatically turns this option on. If you need your code to start
faster under -T (taint) checking, you'll need to turn this option off
manually. Only do this if you are not worried about security risks. See
the UNSAFE shortcut below.
Makes Inline build (compile) the source code every time the program is
run. The default is 0. See the FORCE shortcut below.
Tells ILSMs that they should dump build messages to the terminal rather than be silent about all the build details.
Tells ILSMs to print timing information about how long each build phase
took. Usually requires Time::HiRes.
Tells Inline to clean up the current build area if the build was
successful. Sometimes you want to DISABLE this for debugging. Default is
1. See the NOCLEAN shortcut below.
Tells Inline to clean up the old build areas within the entire Inline
DIRECTORY. Default is 0. See the CLEAN shortcut below.
Tells Inline to print various information about the source code. Default
is 0. See the INFO shortcut below.
Tells Inline to print Version info about itself. Default is 0. See the
VERSION shortcut below.
Puts Inline into 'REPORTBUG' mode, which is what you want if you desire to report a bug.
This option tells Inline whether to print certain warnings. Default is 1.
This is a list of all the shorcut configuration options currently available for Inline. Specify them from the command line when running Inline scripts.
perl -MInline=NOCLEAN inline_script.pl
or
perl -MInline=Info,force,NoClean inline_script.pl
You can specify multiple shortcuts separated by commas. They are not case sensitive. You can also specify shorcuts inside the Inline program like this:
use Inline 'Info', 'Force', 'Noclean';
NOTE:
If a 'use Inline' statement is used to set shortcuts, it can not be
used for additional purposes.
STDERR.
Among the things that get printed is a list of which Inline functions
were successfully bound to Perl.
Puts Inline into 'REPORTBUG' mode, which does special processing when you want to report a bug. REPORTBUG also automatically forces a build, and doesn't clean up afterwards. This is so that you can tar and mail the build directory to me. REPORTBUG will print exact instructions on what to do. Please read and follow them carefully.
NOTE: REPORTBUG informs you to use the tar command. If your system does not have tar, please use the equivalent zip command.
Inline::MakeMaker. See the
section below on how to create modules with Inline.
-T. Only use this if you are sure the
environment is safe.
-T switch.
Writing CPAN modules that use C code is easy with Inline. Let's say that
you wanted to write a module called Math::Simple. Start by using the
following command:
h2xs -PAXn Math::Simple
This will generate a bunch of files that form a skeleton of what you
need for a distributable module. (Read the h2xs manpage to find out what
the options do) Next, modify the Simple.pm file to look like this:
package Math::Simple;
$VERSION = '1.23';
use base 'Exporter';
@EXPORT_OK = qw(add subtract);
use strict;
use Inline C => 'DATA',
VERSION => '1.23',
NAME => 'Math::Simple';
1;
__DATA__
=pod
=cut
__C__
int add(int x, int y) {
return x + y;
}
int subtract(int x, int y) {
return x - y;
}
The important things to note here are that you must specify a NAME
and VERSION parameter. The NAME must match your module's package
name. The VERSION parameter must match your module's $VERSION
variable and they must be of the form /^\d\.\d\d$/.
NOTE: These are Inline's sanity checks to make sure you know what you're doing before uploading your code to CPAN. They insure that once the module has been installed on someone's system, the module would not get automatically recompiled for any reason. This makes Inline based modules work in exactly the same manner as XS based ones.
Finally, you need to modify the Makefile.PL. Simply change:
use ExtUtils::MakeMaker;
to
use Inline::MakeMaker;
When the person installing Math::Simple does a "make", the
generated Makefile will invoke Inline in such a way that the C code will
be compiled and the executable code will be placed into the ./blib
directory. Then when a "make install" is done, the module will be
copied into the appropiate Perl sitelib directory (which is where an
installed module should go).
Now all you need to do is:
perl Makefile.PL
make dist
That will generate the file Math-Simple-0.20.tar.gz which is a
distributable package. That's all there is to it.
IMPORTANT NOTE: Although the above steps will produce a workable module, you still have a few more responsibilities as a budding new CPAN author. You need to write lots of documentation and write lots of tests. Take a look at some of the better CPAN modules for ideas on creating a killer test harness. Actually, don't listen to me, go read these:
perldoc perlnewmod
http://www.cpan.org/modules/04pause.html
http://www.cpan.org/modules/00modlist.long.html
In reality, Inline just automates everything you would need to do if you were going to do it by hand (using XS, etc).
Inline performs the following steps:
Inline gets the source code from your script or module with a statements like the following:
use Inline C => "Source-Code";
or
use Inline;
bind Inline C => "Source-Code";
where C is the programming language of the source code, and
Source-Code is a string, a file name, an array reference, or the
special 'DATA' keyword.
Since Inline is coded in a "use" statement, everything is done during
Perl's compile time. If anything needs to be done that will affect the
Source-Code, it needs to be done in a BEGIN block that is
before the "use Inline ..." statement. If you really need to
specify code to Inline at runtime, you can use the bind() method.
Source code that is stowed in the 'DATA' section of your code, is
read in by an INIT subroutine in Inline. That's because the DATA
filehandle is not available at compile time.
Inline only needs to build the source code if it has not yet been built.
It accomplishes this seemingly magical task in an extremely simple and
straightforward manner. It runs the source text through the
Digest::MD5 module to produce a 128-bit "fingerprint" which is
virtually unique. The fingerprint along with a bunch of other
contingency information is stored in a .inl file that sits next to
your executable object. For instance, the C code from a script called
example.pl might create these files:
example_pl_3a9a.so
example_pl_3a9a.inl
If all the contingency information matches the values stored in the
.inl file, then proceed to step 8. (No compilation is necessary)
At this point Inline knows it needs to build the source code. The first thing to figure out is where to create the great big mess associated with compilation, and where to put the object when it's done.
By default Inline will try to build and install under the first place that meets one of the following conditions:
A) The DIRECTORY= config option; if specified
B) The PERL_INLINE_DIRECTORY environment variable; if set
C) .Inline/ (in current directory); if exists and $PWD != $HOME
D) bin/.Inline/ (in directory of your script); if exists
E) ~/.Inline/; if exists
F) ./_Inline/; if exists
G) bin/_Inline; if exists
H) Create ./_Inline/; if possible
I) Create bin/_Inline/; if possible
Failing that, Inline will croak. This is rare and easily remedied by just making a directory that Inline will use;
If the module option is being compiled for permanent installation, then
Inline will only use ./_Inline/ to build in, and the
$Config{installsitearch} directory to install the executable in. This
action is caused by Inline::MakeMaker, and is intended to be used in
modules that are to be distributed on the CPAN, so that they get
installed in the proper place.
Parse::RecDescent to parse through your
chunks of C source code and look for things that it can create run-time
bindings to. In C it looks for all of the function definitions and
breaks them down into names and data types. These elements are used to
correctly bind the C function to a Perl subroutine. Other Inline
languages like Python and Java actually use the python and javac
modules to parse the Inline code.
Makefile.PL.
perl Makefile.PL && make &&
make test && make install". If something goes awry, Inline will croak
with a message indicating where to look for more info.
NOCLEAN shortcut option will also stop Inline from cleaning up.
For C (and C++), Inline uses the DynaLoader::bootstrap method to pull
your external module into Perl space. Now you can call all of your
external functions like Perl subroutines.
Other languages like Python and Java, provide their own loaders.
For information about using Inline with C see Inline::C.
For sample programs using Inline with C see Inline::C-Cookbook.
For "Formerly Answered Questions" about Inline, see Inline-FAQ.
For information on supported languages and platforms see Inline-Support.
For information on writing your own Inline Language Support Module, see Inline-API.
Inline's mailing list is inline@perl.org
To subscribe, send email to inline-subscribe@perl.org
When reporting a bug, please do the following:
- Put "use Inline REPORTBUG;" at the top of your code, or use the command line option "perl -MInline=REPORTBUG ...". - Run your code. - Follow the printed directions.
Brian Ingerson <INGY@cpan.org>
Neil Watkiss <NEILW@cpan.org> is the author of Inline::CPP,
Inline::Python, Inline::Ruby, Inline::ASM, Inline::Struct
and Inline::Filters. He is known in the innermost Inline circles as
the "Boy Wonder".
Copyright (c) 2000, 2001, 2002. Brian Ingerson. All rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
See http://www.perl.com/perl/misc/Artistic.html