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Can't install DBIx::Class because DBD::mysql is three years out of date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 [email_address] http://mag-sol.com