Why do so many companies
reinvent
well-known CPAN modules badly and end up writing far too much code?

I'm a
freelancer

I work with
many different companies

Ten years
Sixteen companies

A LOT of code

In many cases
it's like they've never heard of CPAN

CPAN
is
good

CPAN
is Perl's
killer app

Modern Perl programming is (often) just plumbing CPAN modules together

Less code
is good

Less code
that you don't have to maintain
is better

Well-tested code is good

Code that is tested by
hundreds of people on dozens of operating systems is better

Why would you ignore all that ready-written, pre-tested code?

Hold
that
thought

Is it
really
that bad?

A straw poll

Who doesn't use DateTime?

Who doesn't use DBIx::Class?

Who doesn't use Template Toolkit?

We are not
typical
Perl users

We read
use.perl

We read
The Perl Review

We go to
Perl Monger meetings

We go to
Perl Conferences

The average
Perl programmer knows less
about CPAN
than we do

They aren't bad programmers

They just
don't follow
the Perl world
as closely
as we do

Perhaps
their job
involves using many different languages

Perhaps
they have
better things
to do with their
time than reading everything on use.perl

Perhaps
they have
a life

To return to
our question

Why would you ignore all that ready-written, pre-tested code?

Reason 1:
People don't know what is on CPAN

Reason 2:
People don't know what is good on CPAN

Not everyone
knows how to extract the jewels
from the crap
on CPAN

The Perl
Echo Chamber strikes again

Be the
CPAN expert
in your
company

Offer training
sessions on
CPAN modules

Draw your
colleagues
into the
echo chamber

Resistance
is
futile

Reason 3:
Not Invented Here

Some companies prefer
their own code over CPAN code

CPAN code is unsupported

Reason 4:
Legacy Code

Newer modules didn't exist
when code
was written

Fair enough
(of course)

But use the
modern modules
in new
development

Refactor
when you have
the chance

Reason 5:
Older versions of required modules

Can't install DBIx::Class because
DBD::mysql
is three years
out of date

Fear of
updating
key modules

Refresh your installed modules regularly

You do have a trustworthy testing environment
I assume

(Tell management that the older versions are no longer supported)

Reason 6:
Sysadmins

Some sysadmins don't like
to install
modules
from CPAN

They prefer their operating system's own packaging system
(deb, rpm, etc)

Find a repository that packages
CPAN modules
for your
operating system

Learn to package CPAN modules
for your
operating system

Also
Sysadmins
like beer

Some vague and
ill thought out conclusions

CPAN
is
good

Use of well-chosen CPAN modules can dramatically cut the amount of code you need to write

Use of well-chosen CPAN modules can dramatically cut the amount of code you need to write

Use of
CPAN modules cut the code you write

Write
less
code

CPAN code
will be
better tested
than your own code

Everyone needs help finding
the good stuff
on CPAN

Evangelise CPAN
at your company

(I find DateTime is a good
starting point)

Mention CPAN
when talking
about successes with management

Your sysadmin
is your friend

(and often a good drinking partner)

Invite me
to laugh at
(and improve)
your codebase

Dave Cross
Magnum Solutions
dave@mag-sol.com
http://mag-sol.com