Last week I explored using the Inline::Perl5 mod­ule to port a short Perl script to Raku while still keep­ing its Perl depen­den­cies. Over at the com­mu­ni­ty, Dave Cross point­ed out that I could get a bit more bang for my buck by let­ting his Feed::Find do the heavy lift­ing instead of WWW::Mechanizes more general-​purpose parsing.

A lit­tle more MetaCPAN inves­ti­ga­tion yield­ed XML::Feed, also main­tained by Dave, and it had the added ben­e­fit of obvi­at­ing my need for XML::RSS by not only dis­cov­er­ing feeds but also retriev­ing and pars­ing them. It also han­dles the Atom syn­di­ca­tion for­mat as well as RSS (hi dax­im!). Putting it all togeth­er pro­duces the fol­low­ing much short­er and clear­er Perl:

#!/usr/bin/env perl

use v5.12; # for strict and say
use warnings;
use XML::Feed;
use URI;

my $url = shift @ARGV || '';

my @feeds = XML::Feed->find_feeds($url);
my $feed  = XML::Feed->parse( URI->new( $feeds[0] ) )
    or die "Couldn't find a feed at $url\n";

binmode STDOUT, ':encoding(UTF-8)';
say $_->title, "\t", $_->link for $feed->entries;

And here’s the Raku version:

#!/usr/bin/env raku

use XML::Feed:from<Perl5>;
use URI:from<Perl5>;

sub MAIN($url = '') {
    my @feeds = XML::Feed.find_feeds($url);
    my $feed  = XML::Feed.parse( @feeds.first ) )
        or exit note "Couldn't find a feed at $url";

    put .title, "\t", .link for $feed.entries;

It’s even clos­er to Perl now, though it’s using the first rou­tine rather than sub­script­ing the @feeds array and leav­ing off the the $_ vari­able name when call­ing meth­ods on it—less punc­tu­a­tion noise often aids read­abil­i­ty. I also took a sug­gest­ed exit idiom from Raku devel­op­er Elizabeth Mattijsen on Reddit to sim­pli­fy the con­tor­tions I was going through to exit with a sim­ple mes­sage and error code.

There are a cou­ple of lessons here:

  • A lit­tle more effort in mod­ule shop­ping pays div­i­dends in sim­pler code.
  • Get feed­back from far and wide to help improve your code. If it’s for work and you can’t release as open-​source, make sure your code review process cov­ers read­abil­i­ty and maintainability.

5 thoughts on “Frenemies part 2: What a difference a (Perl) module makes

  1. For short pro­grams with no oth­er sub­rou­tines, I pre­fer using unit sub MAIN(signature here);, which treats the entire file as the body of the MAIN sub­rou­tine and saves you some curlies and an inden­ta­tion lev­el while still get­ting you the auto­mat­ic argu­ment pars­ing that comes from declar­ing a MAIN sub.

  2. @natalie #Perl to #RakuLang isn’t nec­es­sar­i­ly an upgrade,” it’s a port to a dif­fer­ent ecosys­tem and lan­guage with some similarities.I did a pair of blog posts last year show­ing how you could start with a small bit of Perl code and then rewrite some of it in Raku while still using Perl CPAN mod­ules:•
    Perl & Raku: Best frenemies—The Phoenix Trap

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