Effective Perl Programming – write better, more idiomatic Perl
[Lexical $_ was removed in v5.24]
Perl 5.10 introduced the given-when feature, a fancier version of the C switch feature. However, it was poorly designed and tested and depended on two other dubious features, the lexical $_ and smart-matching. Parts of this feature are salvageable, but you should avoid the literal given (and probably the lexical $_ and the smart matching, but I’ll skip those for this Item). Continue reading “Use for() instead of given()”
Perl lets you override the effects of warn and die by redefining the signals that Perl sends when you call those functions. You probably don’t want to use the signal from die, though, since it might mean a couple of different things. Continue reading “Override die with END or CORE::GLOBAL::die”
The Test Anything Protocol, or just TAP, is the formalization of Perl 5’s test structure from the Test::Harness module. Either Andreas König or Tim Bunce (they don’t remember which one of them did it) created the module, but they can’t remember who did what or when. The Changes file for the Test-Harness starts in seriousness in 2006, around the time that people started working on the next generation of Perl’s testing backend, despite it existing for several years before that. Now TAP is semi-formalized (and IETF RFC is in the works) and has it’s own website at testanything.org. Continue reading “Understand the Test Anything Protocol”
Is your object-oriented module subclassable? Do you know that from testing or are you just guessing? Setting aside other Perl programmers reaching into your package and redefining your subroutines, there are some basic things you can do to ensure that you’ve made life unhard for the people you want to extend your classes. Continue reading “Pass the empty subclass test”
The Git distributed version control system is very popular in with Perlers, and even if you aren’t using it for your own project, you should know how to do simple things with it so you can interact with the most active parts of the community. It’s not that hard. Not only that, many Perl projects are on Github, and it’s something else you’ll know when you go to your next interview. Continue reading “Use Git::CPAN::Patch to make quick patches to CPAN distributions”
Perl will autovivify complex data structures when you use them as if they already exist. This feature saves you a lot of annoying work defining structures that you intend to use. However, this also means that Perl might create data structures that you don’t intend to use in code that isn’t just assigning values. Continue reading “Understand autovivification”
Perl 5.10 introduced a flexible method resolution order mechanism. Instead of Perl’s default order (see Understand Perl’s default inheritance model), you can try something less stupid by using the mro pragma to specify which order perl. Continue reading “Use the C3 method resolution order in multiple inheritance”
There’s a popular internet meme that says a July will only ever have five complete weekends, a Friday-Saturday-Sunday triplet, only every 823 years. To programmers, that might seem just absurd, but a lot of people believe it without thinking about it: that’s how it becomes the popular internet meme. Continue reading “Use DateTime to disprove internet calendar memes”
How would you get more than one line from a file? In the original Effective Perl blog that Joseph set up to support the first edition of Effective Perl Programming, he shows two possible techniques. One uses a foreach: Continue reading “Read a few lines from a file”
Byte-order modifiers are one of the Perl 5.10 features farther along in perl5100delta, after the really big features. To any pack format, you can append a < or a > to specify that the format is little-endian or big-endian, respectively. This allows you to handle endianness in the formats that don’t have specify versions for each architecture already, as well as apply endianness to groups. Continue reading “Use the > and < pack modifiers to specify the architecture"