Originally published at Perl Weekly 746

Hi there,

YAPC::Fukuoka 2025 is happening on 14-15 Nov 2025.

I'm also excited about LPW 2025. From our latest update from the organisers, the event is moving forward. They're making every effort to ensure it happens, which is no small feat given the short notice. What's particularly remarkable is that they're managing this with just a two-person team.

They truly need our support, so please do reach out if you can help. The organisers are currently seeking sponsors, volunteers and speakers. I've tentatively submitted a talk proposal myself.

Hopefully, I'll see you all at the event. The venue is expected to be confirmed this week. For the latest updates, please check the website.

Enjoy rest of the newsletter.

--
Your editor: Mohammad Sajid Anwar.

Announcements

YAPC::Fukuoka 2025

It's 2 days event, 14-15 Nov 2025. YAPC::Fukuoka 2025 will be the first time the event is held in Kyushu since YAPC::Fukuoka 2017 HAKATA.

The corner of Gabor

A couple of entries sneaked in by Gabor.

Adding tests to legacy Perl code

Online live-coding event.

Articles

Implementing Bitcoin in a dead language

An exceptional piece of technical writing that balances satire, technical depth and human vulnerability while showcasing significant software engineering accomplishment. It now implements BIP340 (Schnorr signatures), BIP341 (spending rules) and BIP342 (script validation).

A polymorphic quine

An exceptional deep dive into esoteric programming concepts that demonstrates profound computer science knowledge and creative problem-solving.

AWS S3 Bucket Events

Back to my favourite topic: AWS. In this post, I am showing how to tackle S3 bucket events using AWS Lambda.

CPAN

App::Test::Generator

This is a major improvement of the fuzz testing framework, a building tool that automatically generates comprehensive test suites from formal specifications.

Grants

PEVANS Core Perl 5: Grant Report for October 2025

Maintaining Perl (Tony Cook) October 2025

The Weekly Challenge

The Weekly Challenge by Mohammad Sajid Anwar will help you step out of your comfort-zone. You can even win prize money of $50 by participating in the weekly challenge. We pick one champion at the end of the month from among all of the contributors during the month, thanks to the sponsor Lance Wicks.

The Weekly Challenge - 347

Welcome to a new week with a couple of fun tasks "Format Date" and "Format Phone Number". If you are new to the weekly challenge then why not join us and have fun every week. For more information, please read the FAQ.

RECAP - The Weekly Challenge - 346

Enjoy a quick recap of last week's contributions by Team PWC dealing with the "Longest Parenthesis" and "Magic Expression" tasks in Perl and Raku. You will find plenty of solutions to keep you busy.

TWC346

For The Weekly Challenge, this is a strong, organised solutions post. Working code for both challenges is provided by Ali, who exhibits a straightforward and useful approach to problem-solving. The answers are clear and accurate.

Parenthesised Magic

This blog post is technically sound, informative and well-written. It successfully illustrates a typical Raku problem-solving technique: beginning with a simple, imperative approach and then refining it into a more idiomatic, succinct and potent functional solution.

Perl Weekly Challenge: Week 346

Jaldhar doesn't just provide solutions but explores multiple approaches for each problem, analysing trade-offs between readability, performance and idiomatic style. The post is rich with technical insights, performance benchmarks and clever algorithmic thinking, making it both educational and intellectually stimulating.

Magic Parentheses

This is an excellent, technically complex post that demonstrates sophisticated Perl programming methods. Jorg exhibits a thorough understanding of mathematical optimization, regex engines and effective algorithm design.

really not inspired!

Welcome back Luca after the break, nice hack about tracking nesting levels in Raku.

Perl Weekly Challenge 346

This is an excellent technical blog post that demonstrates deep algorithmic creativity and strong problem-solving skills. It's a genuinely novel approach that demonstrates deep understanding of the problem domain rather than just implementing standard algorithms.

Recursive Parentheses - But no Recursive Magic

This is a solid and insightful write-up by Matthias - concise, technically sound and pedagogically clear.

Whoa-oh-oh! Sing about parens!

This is a superb technical blog post that exhibits profound pedagogical understanding and remarkable programming proficiency in several languages.

(Magic)

This post blends practical implementation knowledge with sophisticated algorithms. Peter demonstrates a solid foundation in computer science and carefully weighs the pros and cons of various strategies.

All Aboard The Magic Parenthesis

This is a solid, practical technical blog post that demonstrates good problem-solving skills across multiple languages.

Longest Expression

Both tasks are implemented correctly, pedagogically and safely. The code favors clarity and correctness over performance, which makes sense for a challenge-focused context.

Rakudo

2025.44 Jimmy Wales on Audrey Tang

This is a high-quality community newsletter that successfully serves both technical and social aspects of the Raku ecosystem. It demonstrates an active, thoughtful community with meaningful technical content and important community developments.

Weekly collections

NICEPERL's lists

Great CPAN modules released last week;
MetaCPAN weekly report.

Events

Perl Maven online: Adding tests to legacy Perl code

November 11, 2025

Paris.pm monthly meeting

November 12, 2025

YAPC::Fukuoka 2025

November 14-15, 2025

London Perl and Raku Workshop

November 29, 2025

Toronto.pm - online - How SUSE is using Perl

December 6, 2025

Paris.pm monthly meeting

December 10, 2025

You joined the Perl Weekly to get weekly e-mails about the Perl programming language and related topics.

Want to see more? See the archives of all the issues.

Not yet subscribed to the newsletter? Join us free of charge!

(C) Copyright Gabor Szabo
The articles are copyright the respective authors.

My fellow contributor @ehuelsmann located a regression since we spun off 2.X from 1.X.

• GitHub perl-workflow release 2.07

The regression was observed by @ehuelsmann and he provided a PR with a fix.

The regression was a change to return values and one of the interesting Perl discussions on whether to return undef or just do return. Anyway the fix reinstates the previous behavior and returns undef.

Here follows the change log for the bug fix release.

2.07 2025-11-08 bug fix release, update not required

Fixed

• Issue: #266 discovered by Erik Huelsmann. A regression introduced with 2.X releases. Fixed via PR: #267 also by Erik Huelsmann

Originally published at Perl Weekly 745

Hi there!

First of all, apologies. Apparently last edition included a link the source of the Perl IDE survey and not the actual Perl IDE Survey itself. This week we hope to provide you with the correct link.

The announcement about the London Perl Workshop might have also been a bit premature as it was still unclear if it will happen at all. I am still unclear about the exact situation, but this is an excellent opportunity for you to step up. Check out the web-site of LPW where you can find the names and the contact information of the organizers. Talk to them and offer your help. Any help. That will increase the chances for this to actually take place. We even received a special announcement exclusive to the readers of the Perl Weekly.

I figured I need to update my web site and emphasize that I help companies deal with legacy code, and that made me think: What does 'legacy code' mean? How is it different from 'existing code' or 'code in production'? Is it a term use in a derogative manner? Does it mean 'code that is in use, but where the authors have disappeared'? Does it mean 'code that I am scared to touch'? Maybe 'code that still makes money, but we are unsure how it works, we need to make changes but we are scared to do'?

I'd love to hear (well, read) what do you think about it. I know I could ask the AI overlord, but I am old-school and I prefer human intelligence.

While we are figuring out how to define legacy code I thought I'll organize an online event in which we'll take a CPAN module and add some tests to it. Register here

In any case, have a nice week!

--
Your editor: Gabor Szabo.

Announcements

Perl IDE survey

After a long hiatus the Perl IDE Survey is back to another round. It will take you about 20 seconds to fill it.

Articles

6 Perl One-Liners to Replace Common Linux Utilities

why for/foreach can't use existing vars?

A lesson in scoping?

OpenAPI Linter

OpenAPI has become the standard for designing, building and documenting RESTful APIs. However, ensuring your OpenAPI specifications are both syntactically correct and follow best practices can be challenging. OpenAPI::Linter brings comprehensive validation and linting capabilities directly into your Perl applications and development workflow, helping you catch issues before they impact your API consumers.

Increasing Code coverage with Gemini

Excellent, showing the prompts help a lot!

Enhance your Gemini code assistance with a PRD document

I made a multiple-insert as well as other methods for Mojo::Pg

ANNOUNCE: Perl.Wiki V 1.33 & Mojolicious.Wiki V 1.08

Ron moved to a retirement village and still coding at 75. Nice.

App::Test::Generator 0.12

App::Test::Generator - Generate fuzz and corpus-driven test harnesses. This module takes a formal input/output specification for a routine or method and automatically generates test cases.

The Weekly Challenge

The Weekly Challenge by Mohammad Sajid Anwar will help you step out of your comfort-zone. You can even win prize money of $50 by participating in the weekly challenge. We pick one champion at the end of the month from among all of the contributors during the month, thanks to the sponsor Lance Wicks.

The Weekly Challenge - 346

Welcome to a new week with a couple of fun tasks "Longest Parenthesis" and "Magic Expression". If you are new to the weekly challenge then why not join us and have fun every week. For more information, please read the FAQ.

RECAP - The Weekly Challenge - 345

Enjoy a quick recap of last week's contributions by Team PWC dealing with the "Peak Positions" and "Last Visitor" tasks in Perl and Raku. You will find plenty of solutions to keep you busy.

TWC345

Code that is clear, effective and useful and that accurately addresses both issues. The solutions demonstrate good Perl fundamentals with straightforward algorithmic approaches.

Last Peak

This is an excellent example of using Raku's special feature set to solve a problem in a stylish, understandable and effective manner. In addition to solving the problem, Arne uses it to illustrate why Raku is a delight for algorithmic and data-centric programming. It is a brilliant pedagogical move to go from a naive to an idiomatic solution.

I Went to the Mountains

Excellent practical Perl programming is demonstrated in this post, with an emphasis on readable, maintainable code that addresses the issue at hand directly. Bob takes a methodical, deliberate approach that is full of the kind of practical judgment that distinguishes good code from great code. The technical content is very interesting because of the conversational tone and cultural allusions.

Perl Weekly Challenge: Week 345

Excellent approach to problem-solving that combines efficient debugging and logical reasoning. By pointing out edge cases, clearing up early misunderstandings and offering comprehensive explanations, Jaldhar exhibits strong analytical abilities.

The Last Peak

This is a thorough, engineering-focused in-depth analysis that places a premium on robustness, accuracy and beautiful API design. It is not merely a solution post. Jorg approaches the challenges with the rigor of a software engineer building production-grade code, not just solving puzzles.

Perl Weekly Challenge 345

A sophisticated, functionally-focused Perl solution that showcases complex programming methods like closures, iterators and functional composition. He tackles the problems with a thorough knowledge of Perl's functional programming features.

Visiting the Peaks

Brilliantly idiomatic Perl that makes use of sophisticated language features to produce succinct, effective and ingenious solutions. Matthias exhibits a thorough comprehension of Perl's contemporary features and functional programming capabilities.

Teach Them How To Say PWC…

This is a philosophical and pedagogical analysis of the Perl Weekly Challenge itself rather than a solution post. The difficulties serve as a starting point for more in-depth conversations about community, learning and the nature of programming expertise.

Peak at the answers

A simple, effective and useful Perl implementation that uses little code to accurately address both issues. Without superfluous abstraction or flourish, Peter concentrates on the fundamental algorithmic requirements. It is an example of "get the job done" programming.

The Weekly Challenge #345

A comprehensive, expertly designed set of solutions with a focus on robustness, extensive testing and unambiguous documentation. Robbie shows how to develop software in a methodical, quality-focused manner.

Position the Visitor

A highly analytical and mathematically complex method that investigates the problems underlying structure. Beyond simple implementation, Roger explores mathematical properties, algorithmic complexity and sophisticated Raku idioms.

Peak Visitors

A simple, useful implementation that puts accuracy and readability ahead of cunning. Simon is refreshingly honest about their comprehension of the issues and exhibits a methodical approach to problem-solving.

Perl Weekly Challenge: 345

A clear, useful Perl implementation that uses simple, readable code to accurately address both issues. Vinod exhibits solid Perl foundations and a pragmatic approach to problem-solving.

Weekly collections

NICEPERL's lists

Great CPAN modules released last week.

Events

Perl Maven online: Adding tests to legacy Perl code

November 11, 2025

Paris.pm monthly meeting

November 12, 2025

London Perl and Raku Workshop

November 29, 2025

Toronto.pm - online - How SUSE is using Perl

December 6, 2025

Paris.pm monthly meeting

December 10, 2025

You joined the Perl Weekly to get weekly e-mails about the Perl programming language and related topics.

Want to see more? See the archives of all the issues.

Not yet subscribed to the newsletter? Join us free of charge!

(C) Copyright Gabor Szabo
The articles are copyright the respective authors.

I found the two tasks this week straight-forward and oddly specific, respectively.

Music: the task titles this week are "Peak Positions" and "Last Visitor", which led me to the refrain "I went to the mountains." It's a reference to Closer to Fine by the Indigo Girls, which references Perl philosophy: "There's more than one answer to these questions pointing me in a crooked line, and the less I seek my source for some definitive, the closer I am to fine."

However, for "Peak Positions", let's go with Ain't No Mountain High Enough by Marvin Gaye; and for "Last Visitor", with it's odd back and forth, how about the venerable Hello, Goodbye by the Beatles.

Task 1: Peak Position

The task

You are given an array of integers, @ints. Find all the peaks in the array. A peak is an element that is strictly greater than its left and right neighbors. Return the indices of all such peak positions.

The thought process

My first thought was to use List::MoreUtils::indexes to test each element, but the edges make it weird. One way or another, they will have to be handled separately. Maybe put a fake element on each end? Do them first and then process the rest? Or test for edges while looping?

My mental model is that the edges of the list fall away into an abyss, so anything outside the list should be below the altitudes given at the edge positions. I suppose it's equally valid to assume that the list is surrounded by huge ice walls (winter is coming).

There are a couple of unspecified anomalies, for which I'm going to take executive decisions:

• Empty list: return an empty list
• Single element: that's one peak at index 0
• Ramp up: (e.g. 7,8,9) the rightmost element is the only peak
• Ramp down: (e.g. 6,5,4) the left-most element is the only peak
• Plateau: (e.g., 7,7,7) No peak, return an empty list. This contradicts my decision for a single element (a plateau of one). Do I contradict myself? Very well then, I contradict myself. (I am large, I contain multitudes.)

The code

sub peakPos(@int)
{
    my @peak = ();
    for my ($i, $n) ( indexed @int )
    {
        my $left  = ( $i == 0     ) ? $n-1 : $int[$i-1];
        my $right = ( $i == $#int ) ? $n-1 : $int[$i+1];
        push @peak, $i if ( $n > $left && $n > $right );
    }
    return \@peak;
}

Notes:

• Once again I chose indexed (anointed as non-experimental in Perl 5.40) for concise and efficient array traversal.
• Each element has a left neighbor and a right neighbor. For the edges, I'm going to conjure up the missing neighbor and make it less, assuming that outside the list is a bottomless void. You know the one -- the one we scream into while we're on mute during Zoom calls.

Task 2: Last Visitor

The task

You are given an integer array @ints where each element is either a positive integer or -1. We process the array from left to right while maintaining two lists:

• @seen: stores previously seen positive integers (newest at the front)
• @ans: stores the answers for each -1

Rules:

• If $ints[i] is a positive number -> insert it at the front of @seen
  • If $ints[i] is -1:
  • Let $x be how many -1s in a row we’ve seen before this one.
  • If $x < len(@seen) -> append seen[x] to @ans
  • Else -> append -1 to @ans

At the end, return @ans.

The thought process

This task description is highly proscriptive. I'm not sure there's anything better to do here than to translate the text into Perl statements.

sub lastVisitor(@int)
{
    my @seen = ();
    my @ans  = ();

    my $x = 0;  # Count of consecutive -1s
    for ( @int )
    {
        if ( $_ > 0 )
        {
            $x = 0;
            unshift @seen, $_;
        }
        else
        {
            if ( $x < @seen )
            {
                push @ans, $seen[$x];
            }
            else
            {
                push @ans, -1;
            }
            $x++;
        }
    }
    return \@ans;
}

Notes: I don't think there's much to add. There's a couple of basic language features being exploited.

• for (@int) -- use the implicit $_ variable for array elements to avoid having to think of a name
• unshift -- put things on the front of a list
• @seen -- in scalar context gives the size of the array (no need for a length())

The only thing tricky here is incrementing and resetting $x so that it correctly counts the consecutive occurrences of -1. Because there was a possibility of error, I of course made that error, but unit tests straightened me out.

Originally published at Perl Weekly 744

Hi there,

We are excited to announce that The Trampery, located on Old Street in London, will host the London Perl Workshop 2025 on November 29, 2025. Bring your thoughts, your code, your queries and your excitement to this next must-attend Perl community event. To help shape the day, the organisers are already taking suggestions from sponsors and the community. We would like to express our gratitude in advance to all of the sponsors who help make this event possible. Our community thrives because of your support; if you or your organisation are interested in sponsorship opportunities, please review the information on the website. This is your chance to interact, learn, share and develop whether you're an experienced Perl hacker, module author, maintainer or someone who is interested in the language's future developments.

The Perl core team released the development release Perl v5.43.4 concurrently with the announcement of the event. This version provides the most recent advancements in Perl's development and is a member of the blead (development) branch. Please find the changes in the perldelta page.

26th Oct marks the 30th anniversary of the Comprehensive Perl Archive Network (CPAN), which has been driving innovation, teamwork and the Perl ecosystem for 30 years. I can still clearly recall my initial feelings of excitement and apprehension when I uploaded a module to CPAN, knowing that it would be instantly mirrored globally. When CPAN was founded in 1995, it was truly revolutionary. Built before GitHub even existed, it gave Perl a superpower that no other language at the time possessed: a global, searchable, installable archive of reusable code. The people who created the archive as well as the archive itself are what most amaze me. CPAN has always been primarily a human network, with volunteers running PAUSE, tireless testers finding bugs before users ever notice them, authors who ship with care and toolsmiths who make installations run more smoothly each year. To celebrate the occassion, I uploaded v0.67 of BankAccount::Validator::UK.

Enjoy rest of the newsletter.

--
Your editor: Mohammad Sajid Anwar.

Announcements

Development release of Perl v5.43.4

This release focuses on Unicode handling improvements and internationalization support.

London Perl Workshop 2025

It's back again, please join us for an exciting informative one day event.

Dancer2 2.0.1 Released

Dancer2 2.0.1 has been released. It's a small maintenance release that fixes a few broken documentation links.

The Perl IDE - Developer Survey 2025 is now live!

After 12 year hiatus, the Perl IDE Developer Survey has returned! Please do take part in the survey.

Articles

Perl in Jupyter Notebook: A Modern Look for a Classic Language

The article is valuable and motivational, especially for people in the Perl community who feel Perl has had less representation in data science / notebooks / ML. It shows convincingly that the building blocks exist and invites people to experiment.

0xblog — About “Perl”, in 2022

This article is inspiring and helpful, in my opinion. Anyone in the Perl community (or nearby) who wants to be reminded of Perl's modern capabilities and feel that it is still relevant should read it.

A palindromic polyglot program in x86 machine code, Perl, shell, and make

Binary Golf Grand Prix is an annual small file format competition, currently in it's sixth year. The goal is to make the smallest possible file that fits the criteria of the challenge.

Beware of Geeks bearing Grifts

Excellent technical writing - accessible deep knowledge, strong literary craft, authentic developer humor and clearly rooted in the Perl ecosystem.

CPAN

Test2::Plugin::SubtestFilter

Test2::Plugin::SubtestFilter released for Perl tests, which allows filtering test targets by subtest name, similar to --testNamePattern in jest and vitest.

The Weekly Challenge

The Weekly Challenge by Mohammad Sajid Anwar will help you step out of your comfort-zone. You can even win prize money of $50 by participating in the weekly challenge. We pick one champion at the end of the month from among all of the contributors during the month, thanks to the sponsor Lance Wicks.

The Weekly Challenge - 345

Welcome to a new week with a couple of fun tasks "Peak Positions" and "Last Visitor". If you are new to the weekly challenge then why not join us and have fun every week. For more information, please read the FAQ.

RECAP - The Weekly Challenge - 344

Enjoy a quick recap of last week's contributions by Team PWC dealing with the "Array Form Compute" and "Array Formation" tasks in Perl and Raku. You will find plenty of solutions to keep you busy.

TWC344

This blog post successfully guides the reader through the process of resolving two programming challenges and is technically sound and well-written. It exhibits sound coding techniques and strong problem-solving abilities. The main strength of the post is its easy-to-understand, step-by-step explanation style, which makes it suitable for programmers of all skill levels.

Form Formation

The post is well structured and easy to follow, introducing the challenge clearly and then solving it step by step. It uses clean, idiomatic Raku, showcasing native language strengths like permutations, MAIN signature validation and concise array/string transformations. The solutions are compact yet readable, demonstrating how expressive Raku can be for problems that would be verbose in other languages.

Pick Up the Pieces

The post provides a clear, correct and well-structured solution using backtracking. It balances readability with reasonable efficiency for small to medium-sized inputs.

Perl Weekly Challenge: Week 344

This is a brief and useful article that emphasizes offering practical solutions with little fanfare. The author demonstrates a get-it-done mentality by using a "one-liner" approach for the first problem and a simple brute-force permutation strategy for the second. The review will draw attention to some crucial scalability and robustness considerations, even though the solutions are functionally correct for the examples provided.

Turning Arrays Into Arrays

The blog post provides clear, concise and idiomatic Perl solutions to the week 344 tasks. The post provides multiple examples for each task, covering various scenarios and edge cases. This helps readers understand the problem's nuances and test their solutions effectively.

Lazyness and too much tasks!

The post is excellent as an educational and practical demonstration of Raku for these algorithmic challenges. It leverages Raku’s expressive features well amd for small to medium inputs, the solutions work effectively.

Perl Weekly Challenge 344

This is a sophisticated and well-engineered set of solutions that demonstrates deep expertise in Perl, particularly with the Perl Data Language (PDL). It provides multiple approaches for each task, showing a thorough understanding of different algorithmic strategies and their trade-offs. The code is professional, robust and well-documented.

Take it to the Limits

This is a superb example of production-quality thinking that goes far beyond typical challenge solutions. Matthias demonstrates exceptional foresight in identifying edge cases and designing scalable, robust algorithms.

A-ray Sunshine!

This technical blog post is incredibly well-written and captivating. It effectively achieves its main objective, which is to guide the reader through a challenging programming problem while elucidating the reasoning behind it, its dead ends and its elegant solution. In technical writing, it's the ideal illustration of "show your work".

Hip, hip, array!

In the great majority of real-world use cases, this solution accurately resolves the issue and is clear, practical and effective. It creates a sophisticated one-liner by utilizing Perl's advantages in handling strings and numbers. The fundamental requirement of the problem—converting between array and numerical representations—is clearly understood by Peter.

The Weekly Challenge #344

For the examples provided, Robbie offers two workable solutions that accurately address the challenge problems. The solutions are straightforward and practical, prioritizing clarity and simplicity over scalability or optimization for edge cases. The code has a clear structure and useful documentation.

All is Array Formation

This blog post goes beyond standard challenge solutions and is incredibly intelligent and sophisticated. In addition to solving the problems, Roger delves into complex computer science ideas and skillfully makes connections between the two seemingly unconnected tasks. The post exhibits expert-level understanding of functional programming paradigms, algorithms and programming language theory.

The one about arrays

This explanation of the Weekly Challenge solutions is clear, easy to understand and useful. Beginners and intermediate developers will find Simon's conversational, tutorial-like style especially approachable. The article emphasizes readability and direct problem-solving over algorithmic optimization, with a focus on concise, practical Perl solutions.

Perl Weekly Challenge: 344

These are clean, practical and clever solutions that demonstrate excellent Perl idioms and pragmatic problem-solving. Vinod favors simplicity and readability while leveraging Perl's unique strengths effectively.

Rakudo

2025.42 Release #186 (2025.10)

Weekly collections

NICEPERL's lists

Great CPAN modules released last week.

Events

Paris.pm monthly meeting

November 12, 2025

London Perl and Raku Workshop

November 29, 2025

Toronto.pm - online - How SUSE is using Perl

December 6, 2025

Paris.pm monthly meeting

December 10, 2025

You joined the Perl Weekly to get weekly e-mails about the Perl programming language and related topics.

Want to see more? See the archives of all the issues.

Not yet subscribed to the newsletter? Join us free of charge!

(C) Copyright Gabor Szabo
The articles are copyright the respective authors.