Bob Ernst discusses the challenges of using the Comprehensive Perl Archive Network (CPAN) and the reasons some developers might avoid it, including issues like lack of root access, complicated licensing, and security concerns. He suggests local mirrors and alternative methods for obtaining Perl modules, and emphasizes the importance of quality control within the Perl ecosystem. The talk highlights common programming problems and how to reinvent solutions in scenarios where CPAN is inaccessible.

1. LIFE WITHOUT CPAN
Reinventing the Wheel
Bob Ernst
BobErnstStl@gmail.com
ST. LOUIS PERL MONGERS
July 17, 2013
Bob Ernst Life Without CPAN

2. Comprehensive Perl Archive Network
http://www.cpan.org/
22,938 Perl modules (and growing!)
10,781 authors (and growing!)
Possibly the best feature of Perl
... and sometimes you can't use it
Bob Ernst Life Without CPAN

3. $677 Million
In 2004, CPAN had 15.4 million lines of code, which would cost
$677,000,000 to develop
http://developers.slashdot.org/story/04/07/30/1229239/cpan-677-million-of-perl
Bob Ernst Life Without CPAN

4. Handy tools
cpan
cpanm
cpanp
perlbrew
Bob Ernst Life Without CPAN

5. Why don't people use CPAN?
And how did I become one of them??
Bob Ernst Life Without CPAN

6. But I don't have root..."
No root access? That is an easy one:
us e l o c a l : : l i b ;
Bob Ernst Life Without CPAN

7. Why is this so complicated?"
CPAN often has objected-oriented Perl
Embarrassment of riches
More & Better module documentation couldn't hurt
Bob Ernst Life Without CPAN

8. I don't have enough disk space..."
Who doesn't have lots of disk space in 2013?
SSD drives - fast, but small
Raspberry Pi
Embedded systems
Shared hosting
Virtual Machines
Disk quotas
Bob Ernst Life Without CPAN

9. NIH - Not Invented Here
Pretty silly, but unfortunately common
Bob Ernst Life Without CPAN

10. Security Concerns
Some organizations are serious about security
What company wrote this software?
You want to connect to the internet??
Bob Ernst Life Without CPAN

11. Local Mirror & Packing
CPAN::Mini
CPAN::Mini::Inject
Pinto
Carton
Bob Ernst Life Without CPAN

12. Licensing
What is this FOSS / open source / shareware / freeware stu?
We need to review that license...
Sometimes it is easier to buy software
Bob Ernst Life Without CPAN

13. Mix of licenses
Most, though not all, modules on CPAN are licensed
under the GNU Public License (GPL) or the Artistic
license
{ CPAN FAQ
Bob Ernst Life Without CPAN

14. GPL
The GNU Public License is a
negative
in some organizations
Bob Ernst Life Without CPAN

15. CPAN::Meta::Spec
agpl_3 GNU Affero General Public License, Version 3
apache_1_1 Apache Software License, Version 1.1
apache_2_0 Apache License, Version 2.0
artistic_1 Artistic License, (Version 1)
artistic_2 Artistic License, Version 2.0
bsd BSD License (three-clause)
freebsd FreeBSD License (two-clause)
gfdl_1_2 GNU Free Documentation License, Version 1.2
gfdl_1_3 GNU Free Documentation License, Version 1.3
gpl_1 GNU General Public License, Version 1
gpl_2 GNU General Public License, Version 2
gpl_3 GNU General Public License, Version 3
lgpl_2_1 GNU Lesser General Public License, Version 2.1
lgpl_3_0 GNU Lesser General Public License, Version 3.0
mit MIT (aka X11) License
mozilla_1_0 Mozilla Public License, Version 1.0
mozilla_1_1 Mozilla Public License, Version 1.1
openssl OpenSSL License
perl_5 The Perl 5 License (Artistic 1 GPL 1 or later)
qpl_1_0 Q Public License, Version 1.0
ssleay Original SSLeay License
sun Sun Internet Standards Source License (SISSL)
zlib zlib License
Bob Ernst Life Without CPAN

16. And...
open_source Other Open Source Initiative (OSI) approved license
restricted Requires special permission from copyright holder
unrestricted Not an OSI approved license, but not restricted
unknown License not provided in metadata
May be hard to get approval!
Bob Ernst Life Without CPAN

17. Missing licenses
16.6% of CPAN uploads this year don't have a license in
META.yml
(Older modules are worse!)
http://cpants.cpanauthors.org/kwalitee/metayml has license
Bob Ernst Life Without CPAN

18. Get the modules without CPAN
Perhaps you have access to another source of modules that is
already approved
ActiveState Perl's PPO
Linux package installer (yum, apt, etc.)
Bob Ernst Life Without CPAN

19. This stu is broken!
Perl CPAN have a strong culture of quality and testing... But
there are buggy modules
Look for recommended modules
http://cpanratings.perl.org/
Check outstanding bug list for modules
Report the bug!
Fix the bug yourself (and share the patch)
Fork the module
Bob Ernst Life Without CPAN

20. Who am I going to call for support?
Submit a bug report
IRC
Perl Monks
Stack Over
ow
Mailing lists
ActiveState
Bob Ernst Life Without CPAN

21. Deploying to Production
No internet access (in secure environments)
Slow installs
Missing dependencies
Broken installs
Bob Ernst Life Without CPAN

22. Building on Quicksand
CPAN modules typically have dependencies, modules are updated
all the time
A

23. x in one module might break the module you are counting on!
Bob Ernst Life Without CPAN

24. Make it solid
perlbrew to get the right version of Perl
CPAN::Mini to get the right version of everything else
Bob Ernst Life Without CPAN

25. You've fought the political battle and lost...
What do you do?
Bob Ernst Life Without CPAN

26. Reinvent the Wheel
Bob Ernst Life Without CPAN

27. You aren't alone
If you google XYZ Perl, you'll

28. nd a lot of questions like:
How do I XYZ in Perl without using CPAN?
Bob Ernst Life Without CPAN

29. XML Parsing
Writing an XML parser is hard work
XML isn't a regular language so it can't be parsed with
regular expressions
But in a pinch...
i f ( $ i n p u t =~ qr f ( t i t l e ) ( . ) (/ t i t l e ) gx
) f
$ t i t l e = $2 ;
g
Bob Ernst Life Without CPAN

30. Date and Time
Date::Manip and Date::Calc are so powerful...
what to do when they aren't available?
Bob Ernst Life Without CPAN

31. The Next Eight Sundays (Date::Calc)
us e Date : : Cal c qw( Add De l ta Days Da t e t o Te x t
Day of Week Today ) ;
my @date = Today ( ) ;
my $ d a y s u n t i l s u n d a y = 7 Day of Week ( @date
) ;
i f ( $ d a y s u n t i l s u n d a y == 0 ) f
$ d a y s u n t i l s u n d a y = 7 ;
g
f o r ( my $ i =0; $i 8; $ i++ ) f
@date = Add De l ta Days ( @date ,
$ d a y s u n t i l s u n d a y ) ;
say Da t e t o Te x t ( @date ) ;
$ d a y s u n t i l s u n d a y = 7 ;
g
Bob Ernst Life Without CPAN

32. The Next Eight Sundays (POSIX)
us e POSIX qw( mktime s t r f t ime ) ;
us e c o n s t a n t f
MDAY = 3 ,
WDAY = 6 ,
g ;
my @date = l o c a l t ime ( t ime ( ) ) ;
f o r (my $ i =0; $i 8; $ i++) f
$dat e [MDAY] += 7 $dat e [WDAY] ;
@date = l o c a l t ime ( mktime ( @date ) ) ;
say s t r f t ime ( %a %d%b%Y , @date ) ;
g
Bob Ernst Life Without CPAN

33. Parallel Processing
Modules like Parallel::Queue are great...
if you have CPAN.
Bob Ernst Life Without CPAN

34. Old Fashion Fork
our @c h i l d r e n = ( ) ;
sub spawn command f
my $command = s h i f t ;
my $pid = f o r k ( ) ;
i f ( $pid ) f
push @c h i l d r e n , $pid ;
g
e l s i f ( $pid == 0 ) f
sys tem ( @f$commandg ) ;
e x i t 0 ;
g
g
Bob Ernst Life Without CPAN

35. Fork continued
f o r ( my $ i =1; $ i = 5 2 ; $ i++ ) f
spawn command ( [ what e v e r , $ i ] ) ;
g
f o r e a c h my $pid ( @c h i l d r e n ) f
wa i t p i d ( $pid , 0 ) ;
g
Bob Ernst Life Without CPAN

36. Core Modules
Don't forget the core modules!
Benchmark
Carp
Cwd
Data::Dumper
File::stat
Getopt::Long
IO::Handle
IO::Socket
Log::Message
Math::BigInt
Memoize
Pod::Usage
POSIX
Test::More
Time::Local
682 altogether!
Bob Ernst Life Without CPAN

37. REMEMBER
There are three great virtues of a programmer:
laziness, impatience and hubris
{ Larry Wall
Be lazy and impatient { use CPAN!
Bob Ernst Life Without CPAN