Saturday, March 23, 2013

Learning Perl5i

I've been looking at the module perl5i, which puts a sideways twist on Perl, eliminating tons of boring boilerplate, and introduce many conveniences. In this case, the i eliminates complexity.

Installing perl5i installs a number of other modules as well, on the other hand life becomes better once they are installed.

If you don't have cpanm or one of the other improved CPAN installers, the simplest way is to install perl5i and its friends using the command

     sudo cpan perl5i

You may need to type in yes to have cpan  install dependencies. Some modules are needed only temporarily during installation, and you are asked whether you want them permanently installed. Perl modules don't take up very much space, so I always go for it. Installation is a bit different on Windows or Linux machines, but you can figure it out, you're a mighty Perl programmer!

One consideration is that major versions of perl5i may change in drastic ways. But you don't include perl5i; what you specify is perl5i::2. The newest module includes perl5i::0 and perl5i::1 as well, so old code is supported until you are ready to upgrade them.

The immediate benefit is that you no longer have to enable strictness. perl5i automatically provides

     use warnings;
  use strict;

So it costs you 14 characters to type

    use perl5i::2;

and straight off the bat it saves you 24 characters ....profit!


Oh, and it automatically activates features say, state and switch.


But wait! There's more! Not only does it slice and dice, it also julienes!

Well, no cutting anything in any shape ... but perl5i DOES provide autodie. If your open() doesn't work, the program dies; if the close() doesn't work, the program dies; if print() or a system() call or unlink() don't work, the program dies with an exception that turns into a string if you don't handle it.

Having a program die is an effective way to trigger in-house failure detection systems, such as Nagios. So simply doing the things you want, without checking return values, becomes a viable way to write a secure program that detects problems. If you need to catch and handle problems, perl5i provides Try::Tiny. There are other attempts at exception handling; any of them would be clearer than using eval. Try::Tiny is small, it does the job, and the intent is clear.

    try {
        open my $h, '<', '/does/not/exist';
    } 
    catch {
        say "the open() died with message $_";
    };

You can also add a finally block, to perform things that need to happen regardless of success or failure. The single weakness is that try is a statement, not a block, so it needs a semi-colon

So that's a major from installing perl5i, and we've barely gotten started.