TweetFollow Us on Twitter


Volume Number: 19 (2003)
Issue Number: 1
Column Tag: Mac OS X


Creating GUI-based apps with Perl

by Rich Morin

Sherm Pendley bills CamelBones as "An Objective-C/Perl bridge framework". The web page goes on to say "CamelBones is a framework that allows many types of Cocoa programs to be written entirely in Perl. It also provides a high-level object-oriented wrapper around an embedded Perl interpreter, so that Cocoa programs written in Objective-C can easily make use of code and libraries written in Perl."

Jumping from the general to the particular, CamelBones allows a Perl scripter to create GUI-based apps, with only a modicum of pain (read, Objective-C :-). Because the scripter can use Interface Builder, the graphic layout is painless, quick, and likely to yield attractive results.


Sherm says that CamelBone's biggest current limitation is inheritance. It's not yet possible to create a Perl sub-class that inherits from an Objective-C sub-class. As a result, CamelBones can't be used for:

  • Document-based applications, which require a subclass of NSDocument.

  • Custom controls and/or cells, which require a subclass of one of the many NSControl or NSCell descendants, respectively.

This limitation will be addressed in the next version (0.3), which Sherm expects to have ready by the time this article is in print. Meanwhile, most of the tasks which could be performed by a cub-class can be handled by a Delegation or Notification callback.

CamelBones has some other problems, at least from my perspective. Because the app needs to be "built" (with Project Builder) rather than simply run, the build time becomes a noticeable part of the edit/test cycle. I think that's just the price we pay for using compilers and linkers (:-).

Also, most of the existing Cocoa documentation assumes that you're using Objective-C. This means that you have to have a reading knowledge of Objective-C, as well as the ability to turn method prototypes and example code into their Perl equivalents. I find this livable, however, and help is on the way for both problems

Getting Started

Assuming that you already have OSX and Apple's Developer Tools installed, adding CamelBones is quite simple. Go to http//, download the distribution, and install it! At this writing, the documentation is still a bit sketchy, but the author plans to improve it Real Soon Now, so it may be in significantly better shape by the time you see it.

The package uses a standard installer, so installation is quite easy. I'd suggest that you choose the "Custom" install, so that you can get the source code (why not?). I haven't looked at the code, but I assume that it's a combination of Objective-C and Perl. Nice to have around, if you get frustrated by some peculiarity or simply become curious about how it all works.

If you are thinking about using CamelBones in a proprietary offering, you may want to look over the license a bit. CamelBones is released under the GNU Project's "Lesser General Public License" (LGPL). Briefly, the LGPL allows your app to use CamelBones without any requirement that the author provide the source code for the application (though with Perl, source distribution is the default case). On the other hand, any changes you make to CamelBones itself must be made available to anyone who gets the "binaries".

Once you have CamelBones installed, I strongly suggest that you skim the documentation and walk through the HowTo examples. As a newcomer to Interface Builder and Project Builder, this taught me a bit about the capabilities and operation of each. Even if you are expert at IB and PB, the examples will give you an idea of what kind of Perl code CamelBones expects.

In brief, however, Perl code for use with CamelBones looks pretty much like Perl code to work with any object-oriented API. Stuff like:

sub sayHello {
    my ($self, $sender) = @_;
    NSLog("Hello, world!");

One peculiarity, discussed in the CamelBones web pages, is that CamelBones doesn't (yet ) provide "toll-free" bridging of Perl hashes and lists to Cocoa's collection classes. Consequently, the Perl code has to deal with the Cocoa collections explicitly. Instead of writing:

my %hash;
my $key     = 'abc';
$hash{$key} = 'def';
printf("key=%s, value=%s\n",
  $key, $hash{$key});

you have to write something like:

my $hash = NSMutableDictionary->alloc->init;
my $key  = 'abc';
$hash->setObject_forKey($key, 'def');
printf("key=%s, value=%s\n",
  $key, $hash->objectForKey($key));

Also, because Objective-C doesn't provide automatic (Perl-style) garbage collection, you may need to explicitly reserve and release any Objective-C objects which you create. This looks pretty tedious, to my Perl-accustomed eyes, but I'm consoled by the facts that (a) I only have to use Cocoa collections to access Cocoa-specific items and (b) relief is said to be on the way.

Packaging Issues

Ease of distribution and installation has been a CamelBones priority from the start. All that the end user needs is a copy of CamelBones.framework. By default, applications look for this in /Library/Frameworks, so the easiest thing to do is to create an installer package that will make sure that the framework can be found there.

But, if a developer wants a drag-and-drop install and is willing to rebuild the framework with the appropriate Project Builder options, the framework can be embedded in the application bundle itself. CPAN (Comprehensive Perl Archive Network) modules can also be included in the application bundle, eliminating another common source of pain for end users of Perl programs.

Version Creep

The CamelBones framework is linked against the Perl interpreter (Version 5.6.0) that is shipped with OSX. Sherm has gotten reports that Perl 5.6.1 works fine, as long as it's compiled and installed identically to the original 5.6.0, but 5.8.0 definitely doesn't. So, if you have added Perl 5.8.0 to your system, you may have to rebuild any CamelBones apps you receive.

As time goes on, Apple is quite likely to release Perl 5.8.0 (or whatever) as an update to OSX. Unless a workaround is found, this will cause all 5.6.0-based CamelBones apps to break. Fortunately, some Very Bright People are looking into the matter, so a fix is likely.


Perl wizard Dan Sugalski is currently writing "Programming Cocoa Applications with Perl" for O'Reilly, but a publication date has not yet been established. The book will cover CamelBones in depth, however, so watch for it! In the meanwhile, Dan promises to put up some example code on the CamelBones web site.

Notwithstanding tha fact that they assume Objective-C usage, most books on Cocoa, IB, and PB are relevant to CamelBones Here are some you might want to look over:

    "Building Cocoa Applications: A Step-by-Step Guide"

    Garfinkel and Mahoney

    O'Reilly and Associates, 2002

    ISBN 0-596-00235-1

    "Cocoa Cookbook for Mac OS X"

    Bill Cheeseman

    Peachpit, 2002

    ISBN 0-201-87801-1

    "Cocoa Programming for Mac OS X"

    Aaron Hillegass

    Addison-Wesley, 2001

    ISBN 0-201-72683-1

    "Learning Cocoa with Objective-C", second edition

    James Duncan Davidson

    O'Reilly and Associates, 2002

    ISBN 0-596-00301-3

There is also a 200+ page rundown on Objective-C, right on your Mac OS X system (/Developer/Documentation/Cocoa/ObjectiveC/ObjC.pdf). You should also consider joining the MacOSX-Perl email list, which covers CamelBones and other Perlish topics on Mac OS X. Send email to to get started.

Although Apple provides documentation on the AppKit and Foundation frameworks, it can be tedious to navigate. So, pick up a copy of Hoshi Takanori's Cocoa Browser app ( This will let you browse the Objective-C method descriptions in a speedy, hierarchically-based manner.

As noted above, you will still have to convert the method synopses into Perl format, but that's life. Actually, I'm actually working on a conversion app, but you'll have to wait until next month to read about it. Until then, happy hacking...

Rich Morin has been using computers since 1970, Unix since 1983, and Mac-based Unix since 1986 (when he helped Apple create A/UX 1.0). When he isn't writing this column, Rich runs Prime Time Freeware (, a publisher of books and CD-ROMs for the Free and Open Source software community. Feel free to write to Rich at


Community Search:
MacTech Search:

Software Updates via MacUpdate

Civilization VI 1.1.0 - Next iteration o...
Sid Meier’s Civilization VI is the next entry in the popular Civilization franchise. Originally created by legendary game designer Sid Meier, Civilization is a strategy game in which you attempt to... Read more
Network Radar 2.3.3 - $17.99
Network Radar is an advanced network scanning and managing tool. Featuring an easy-to-use and streamlined design, the all-new Network Radar 2 has been engineered from the ground up as a modern Mac... Read more
Quicken 5.5.6 - Complete personal financ...
Quicken makes managing your money easier than ever. Whether paying bills, upgrading from Windows, enjoying more reliable downloads, or getting expert product help, Quicken's new and improved features... Read more
Civilization VI 1.1.0 - Next iteration o...
Sid Meier’s Civilization VI is the next entry in the popular Civilization franchise. Originally created by legendary game designer Sid Meier, Civilization is a strategy game in which you attempt to... Read more
Network Radar 2.3.3 - $17.99
Network Radar is an advanced network scanning and managing tool. Featuring an easy-to-use and streamlined design, the all-new Network Radar 2 has been engineered from the ground up as a modern Mac... Read more
Printopia 3.0.8 - Share Mac printers wit...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad, or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
ForkLift 3.2.1 - Powerful file manager:...
ForkLift is a powerful file manager and ferociously fast FTP client clothed in a clean and versatile UI that offers the combination of absolute simplicity and raw power expected from a well-executed... Read more
BetterTouchTool 2.417 - Customize multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Little Snitch 4.0.6 - Alerts you about o...
Little Snitch gives you control over your private outgoing data. Track background activity As soon as your computer connects to the Internet, applications often have permission to send any... Read more
Google Chrome 65.0.3325.181 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more

Latest Forum Discussions

See All

The best games that came out for iPhone...
It's not a huge surprise that there's not a massive influx of new, must-buy games on the App Store this week. After all, GDC is happening, so everyone's busy at parties and networking and dying from a sinister form of jetlag. That said, there are... | Read more »
Destiny meets its mobile match - Everyth...
Shadowgun Legends is the latest game in the Shadowgun series, and it's taking the franchise in some interesting new directions. Which is good news. The even better news is that it's coming out tomorrow, so if you didn't make it into the beta you... | Read more »
How PUBG, Fortnite, and the battle royal...
The history of the battle royale genre isn't a long one. While the nascent parts of the experience have existed ever since players first started killing one another online, it's really only in the past six years that the genre has coalesced into... | Read more »
Around the Empire: What have you missed...
Oh hi nice reader, and thanks for popping in to check out our weekly round-up of all the stuff that you might have missed across the Steel Media network. Yeah, that's right, it's a big ol' network. Obviously 148Apps is the best, but there are some... | Read more »
All the best games on sale for iPhone an...
It might not have been the greatest week for new releases on the App Store, but don't let that get you down, because there are some truly incredible games on sale for iPhone and iPad right now. Seriously, you could buy anything on this list and I... | Read more »
Everything You Need to Know About The Fo...
In just over a week, Epic Games has made a flurry of announcements. First, they revealed that Fortnite—their ultra-popular PUBG competitor—is coming to mobile. This was followed by brief sign-up period for interested beta testers before sending out... | Read more »
The best games that came out for iPhone...
It's not been the best week for games on the App Store. There are a few decent ones here and there, but nothing that's really going to make you throw down what you're doing and run to the nearest WiFi hotspot in order to download it. That's not to... | Read more »
Death Coming (Games)
Death Coming Device: iOS Universal Category: Games Price: $1.99, Version: (iTunes) Description: --- Background Story ---You Died. Pure and simple, but death was not the end. You have become an agent of Death: a... | Read more »
Hints, tips, and tricks for Empires and...
Empires and Puzzles is a slick match-stuff RPG that mixes in a bunch of city-building aspects to keep things fresh. And it's currently the Game of the Day over on the App Store. So, if you're picking it up for the first time today, we thought it'd... | Read more »
What You Need to Know About Sam Barlow’s...
Sam Barlow’s follow up to Her Story is #WarGames, an interactive video series that reimagines the 1983 film WarGames in a more present day context. It’s not exactly a game, but it’s definitely still interesting. Here are the top things you should... | Read more »

Price Scanner via

Thursday roundup of the best 13″ MacBook Pro...
B&H Photo has new 2017 13″ MacBook Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only. Their prices are the lowest available for... Read more
Sale: 9.7-inch 2017 WiFi iPads starting at $2...
B&H Photo has 9.7″ 2017 WiFi Apple iPads on sale for $40 off MSRP for a limited time. Shipping is free, and pay sales tax in NY & NJ only: – 32GB iPad WiFi: $289, $40 off – 128GB iPad WiFi: $... Read more
Roundup of Certified Refurbished iPads, iPad...
Apple has Certified Refurbished 9.7″ WiFi iPads available for $50-$80 off the cost of new models. An Apple one-year warranty is included with each iPad, and shipping is free: – 9″ 32GB WiFi iPad: $... Read more
Back in stock! Apple’s full line of Certified...
Save $300-$300 on the purchase of a 2017 13″ MacBook Pro today with Certified Refurbished models at Apple. Apple’s refurbished prices are the lowest available for each model from any reseller. A... Read more
Wednesday deals: Huge sale on Apple 15″ MacBo...
Adorama has new 2017 15″ MacBook Pros on sale for $250-$300 off MSRP. Shipping is free, and Adorama charges sales tax in NJ and NY only: – 15″ 2.8GHz Touch Bar MacBook Pro Space Gray (MPTR2LL/A): $... Read more
Apple offers Certified Refurbished Series 3 A...
Apple has Certified Refurbished Series 3 Apple Watch GPS models available for $50, or 13%, off the cost of new models. Apple’s standard 1-year warranty is included, and shipping is free. Numerous... Read more
12″ 1.2GHz Space Gray MacBook on sale for $11...
B&H Photo has the Space Gray 12″ 1.2GHz MacBook on sale for $100 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 12″ 1.2GHz Space Gray MacBook: $1199 $... Read more
Mac minis available for up to $150 off MSRP w...
Apple has restocked Certified Refurbished Mac minis starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: – 1.4GHz Mac mini: $419 $80 off MSRP – 2.6GHz Mac... Read more
Back in stock: 13-inch 2.5GHz MacBook Pro (Ce...
Apple has Certified Refurbished 13″ 2.5GHz MacBook Pros (MD101LL/A) available for $829, or $270 off original MSRP. Apple’s one-year warranty is standard, and shipping is free: – 13″ 2.5GHz MacBook... Read more
Apple restocks Certified Refurbished 2017 13″...
Apple has Certified Refurbished 2017 13″ MacBook Airs available starting at $849. An Apple one-year warranty is included with each MacBook, and shipping is free: – 13″ 1.8GHz/8GB/128GB MacBook Air (... Read more

Jobs Board

Payments Counsel - *Apple* Pay (payments, c...
# Payments Counsel - Apple Pay (payments, credit/debit) Job Number: 112941729 Santa Clara Valley, California, United States Posted: 26-Feb-2018 Weekly Hours: 40.00 Read more
Firmware Engineer - *Apple* Accessories - A...
# Firmware Engineer - Apple Accessories Job Number: 113452350 Santa Clara Valley, California, United States Posted: 28-Feb-2018 Weekly Hours: 40.00 **Job Summary** Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 113501424 Norman, Oklahoma, United States Posted: 15-Feb-2018 Weekly Hours: 40.00 **Job Summary** Are you passionate about Read more
*Apple* Inc. Is Look For *Apple* Genius Te...
Apple Inc. Is Look For Apple Genius Technical Customer Service Minneapolis Mn In Minneapolis - Apple , Inc. Apple Genius Technical Customer Service Read more
*Apple* Genius Technical Customer Service Co...
Apple Genius Technical Customer Service Columbus Oh Apple Inc. - Apple , Inc. Apple Genius Technical Customer Service Columbus Oh - Apple , Inc. Job Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.