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Sat, 31 Dec 2011

Perl 6 in 2011 - A Retrospection

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The change of year is a good occasion to look back. Here I want to reflect on the development of Perl 6, its compilers and ecosystem.

At the start of the year, masak's Perl 6 Coding Contest continued from 2010, concluding in the announcement of the winner. I must admit that I still haven't read all the books I won :-)


2011 was a rather quiet year in terms of spec changes; they were a mixture of responses to compiler writer and user feedback, and some simplifications and cleanups.

Positional parameters used to be allowed to be called by name; this feature is now gone. That both makes the signature binder simpler, and removes accidental dependencies on names that weren't meant to be public. Read the full justification for more background.

A small change that illustrates the cleanup of old, p5-inherited features was the change that made &eval stop catching exceptions. There is really no good reason for it to catch them, except Perl 5 legacy.

say now uses a different stringification than print. The reasoning is that print is aimed at computer-readable output, whereas say is often used for debugging. As an example, undefined values stringify to the empty string (and produce a warning), whereas say calls the .gist method on the object to be said, which produces the type name on undefined values.

An area that has been greatly solidified due to implementation progress is Plain Old Documentation or Pod. Tadeusz Sośnierz' Google Summer of Code project ironed out many wrinkles and inconsistencies, and changed my perception of this part of the spec from "speculative" to "under development".


Rakudo underwent a huge refactoring this year; it is now bootstrapped by a new compiler called "nqp", and uses a new object model (nom).

It allows us to gain speed and memory advantages from gradual typing; for example the mandelbrot fractral generator used to take 18 minutes to run on a machine of mine, and now takes less than 40 seconds. Speedups in other areas are not as big, but there is still much room for improvement in the optimizer.

With the nom branch came support for different object representations. It makes it possible to store object attributes in simple C-like structs, which in turn makes it much easier and more convenient to interoperate with C libraries.

Tadeusz' work on Pod gave Rakudo support for converting Pod to plain text and HTML, and attach documentation objects to routines and other objects.

Rakudo now also has lazy lists, much better role handling, typed exceptions for a few errors, the -n and -p command line options, support for big integers, NFA-based support for proto regexes and improvements to many built-in functions, methods and operators.


It is hard to accurately summarize the development of Niecza in a few sentences; instead of listing the many, many new features I should give an impression on how it feels and felt for the user.

At the start of 2011, programming in niecza was a real adventure. Running some random piece of Perl 6 code that worked with Rakudo rarely worked, most of the time it hit a missing built-in, feature or bug.

Now it often just works, and usually much faster than in Rakudo. There are still some missing features, but Stefan O'Rear and his fellow contributors work tirelessly on catching up to Rakudo, and it some areas Niecza is clearly ahead (for example Unicode support in regexes, and longest-token matching).

Since Niecza is implemented on top of the Common Language Runtime (CLR) (which means .NET or mono), it makes it easy to use existing CLR-based libraries. Examples include an interactive fractal generator and a small Tetris game in Perl 6.


Perlito aims to be a minimal compiler with multiple backends, which can be used for embedding and experimenting with Perl 6. It had several releases in 2011, and has interesting features like a Javascript backend.


The presence of two usable compilers (and in the case of Rakudo, two viable but very different branches) has led to many questions about the different compilers. The new Perl 6 Compiler Feature matrix tries to answer the questions about the state of the implemented features in the compilers.

With Panda we now have a module installer that actually works with Rakudo. It still has some lengths to go in terms of stability and feature completeness, but it is fun to work with.

The new Perl 6 Modules page gives an overview of existing Perl 6 modules; we hope to evolve it into a real CPAN equivalent.


This year we had another Perl 6 Advent Calendar, with much positive feedback both from the Perl 6 community and the wider programming community.

We were also happy to welcome several new prolific contributors to the Perl 6 compilers and modules. The atmosphere in the community still feels relaxed, friendly and productive -- I quite enjoy it.

The year ends like it started: with a Perl 6 Coding Contest. This is a good opportunity to dive into Perl 6, provide feedback to compiler writers, and most of all have fun.

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