How Perl::Critic Facilitates
Code Best Practices

Chris Dolan

MediaLandscape Software

cdolan@cpan.org

What is Perl::Critic?

Static source code analyzer

• Like an extendable lint for Perl
• As opposed to strict.pm which is a runtime live code analyzer
• Helps find potential bugs, bad practices and style non-compliance
• Easily automated via Test::Perl::Critic

by Jeffrey Ryan Thalhammer (THALJEF)

Motivation

• Inspired by Damian Conway's book, Perl Best Practices
• TIMTOWTDI, but many ways are suboptimal
  • Bugs
  • Performance
  • Readability
  • Cargo cult
• But optimizing while coding is hard

→ Use code to optimize for you!

Policies

• 78 policy modules implemented, 48 of them from PBP
• Adding a new one is not difficult
• Loaded via Module::Pluggable

Usage

Usage

Configuration

Create a ~/.perlcriticrc file

[-CodeLayout::RequireTidyCode]
[-ControlStructures::ProhibitCStyleForLoops]
[-Documentation::RequirePodAtEnd]
[-Documentation::RequirePodSections]
[-Miscellanea::RequireRcsKeywords]
[-NamingConventions::ProhibitMixedCaseSubs]

[ControlStructures::ProhibitCascadingIfElse]
max_elsif = 3

Making Exceptions

Perl::Critic has flags to ignore special cases

• ## no critic at the end of a line
• Lexical block:
  ## no critic
... code ...
## use critic
• Accepts an optional substring to filter

  $email = 'foo@bar.com'; ## no critic(RequireInterpolation)

  sub _calc_xml_paths {  ## no critic(ExcessComplexity)
     ... lots of code ...
  }

Learn more

• http://search.cpan.org/dist/Perl-Critic
• http://perlcritic.tigris.org
• dev-subscribe@perlcritic.tigris.org

And introducing P::C testing via the web: http://perlcritic.com