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Announce: Rakudo Perl 6 compiler, Release #127 (2018.10)

On behalf of the Rakudo development team, I’m very happy to announce the October 2018 release of Rakudo Perl 6 #127. Rakudo is an implementation of Perl 6 on the Moar Virtual Machine[^1].

This release implements the 6.c version of the Perl 6 specifications. It includes bugfixes and optimizations on top of the 2015.12 release of Rakudo.

Upcoming releases in 2018 will include new functionality that is not part of the 6.c specification, available with a lexically scoped pragma. Our goal is to ensure that anything that is tested as part of the 6.c specification will continue to work unchanged. There may be incremental spec releases this year as well.

The tarball for this release is available from

Please note: This announcement is not for the Rakudo Star distribution[^2] — it’s announcing a new release of the compiler only. For the latest Rakudo Star release, see

The changes in this release are outlined below:

New in 2018.10:

    • This is the first Rakudo release that comes with an additional JS backend. See 6pad project for running Perl 6 code directly in your browser.
  • Deprecations:
    • Deprecated gethostname() in favor of $*KERNEL.hostname [f7fa5185]
  • Fixes:
    • Fixed/improved divide-by-zero errors in Rational.floor/.ceiling/.Str [a639fa9c][6d70346c]
    • Fixed semantics of [Nil] [88e6de22]
    • Fixed issue with custom bless method [64137bd2]
    • Made nativecall's postcircumfix:<[ ]> return containers [be2d4cb4]
    • Fixed hash descriptor when doing Hash[Int].new [9acbf000][ea710414]
    • Nil is now allowed in initialization and assignment of hashes [f61ba41a][605bcb39][7e86d4e3]
    • Fixed ContainerDescriptor for arrays with a dimension of three [a2e78ec8]
    • Fixed indexing of shaped arrays with a dimension higher than 3 [0307c366]
    • .in-timezones value is now coerced to Int [c8438e6a]
    • Stub methods from roles are now verified [fd5d5bdf]
    • Fixed double-closing of handles in IO::Handle.lines when :close and $limit are used [6edb142f]
    • Fixed closing of handles in IO::Handle.lines when $limit is used [c1c75740]
    • Consistified Rat.base to fail instead of throw [a804ab57]
    • Fixed enforcing of return constraints on multi method stubs [abba67b2]
    • Various improvements to produced messages [cc2fcc9a][560e94ef] [bf10f4c5][243a2f01][7d02b949][9894eda5][0243275d]
  • Additions:
    • [6.d] Constructs $()/@()/%() no longer have any $/-related magic [bb88a032]
    • [6.d] DefiniteHOWs' (type smileys) default default is now the base type [38b198c9]
    • Zero-Denominator Rationals are now normalized on creation [671c4115] [75ec2248]
    • Made my @a is List = 1,2,3,4 work [2bdf2b35]
    • Using is Type on @ and % attributes is now allowed [b537ce2e]
    • Added a BOM on open for utf16 filehandles [959b89cf][479348f3]
    • Added initial support for Unicode 11.0 [5c272ee4]
    • Pluggable MAIN interface refactored, documented and tested [f234b9af][35f3d83d][7c9b2955][33c24153][8c3a4131][fbfccfa2]][341190e2][24413b5f[2c43d2bf]
    • Usage message now limits itself to partially matching candidates [0d1be77e]
    • Added additional dashed variants for utf16le and utf16be [4307996a]
    • Added Parameter.coerce_type method [0243275d]
    • Added Code.cando method to allow for .cando on all Callables [45eeab78][69533b50]
  • Removals:
    • Removed --encoding support [bea08ec6][31b19d09]
  • Efficiency:
    • Made Hash.push/append between 1.2x and 1.4x as fast [12cfde2a]
    • Made "".ord orders of magnitude faster [b22edce4]
    • Made == with Rationals up to 1.55x as fast [c5a2eb81]
    • Made Rational === Rational 2.47x as fast [97e8413b]
    • Made many cases of for (range-like things) up to 150x as fast [2dd02751][645eeb52][dfd6450d][49baea70][89787028][2af789d7]
    • Made [42] not allocate anything anymore [8c4546bb]
    • Made [@a] and [1,2,3] about 1.4x as fast [e430813f]
    • Made Array.List coercion 1.5x as fast [3d405e89]
    • Made .isa about 2x as fast [4e8740c8]
    • Made infix:<%%> 10.42x as fast on natives [3d161a56]
    • Other minor optimizations [464a86b1][ab83b9d8][8cc3d5d7][b107cda5]
  • Internal:
    • Made make an only [369068ae]
    • Added skip-one method to appropriate PredictiveIterators [e54885e5]
    • More things are now initialized at setting compile time [06dfbf02][688cbac1][92735770]
    • Simplified initialization of CompUnit::RepositoryRegistry [0425d927][8e1cd01a]
    • Introduced IterationBuffer.List [8c10da6a]
    • Use nqp::create for IterationBuffer instead of .new [84311b77]
    • Made sure .STORE only works on instances of mixy/baggy types [9daac683]
    • Added $*INSIDE-EVAL to mark that we're inside an EVAL [73b7c603]

The following people contributed to this release:

Zoffix Znet, Elizabeth Mattijsen, Paweł Murias, JJ Merelo, Tom Browder, Bart Wiegmans, Jonathan Worthington, Will "Coke" Coleda, Aleks-Daniel Jakimenko-Aleksejev, Samantha McVey, thebooort, Juan Julián Merelo Guervós, Ben Davies, Fernando Correa de Oliveira, Timo Paulssen, Daniel Green, MorayJ, Valentin Anger, threadless-screw, Jeremy Studer, Nick Logan, finanalyst, Alexander, Amir Aharoni, Claudio Ramirez, Luis F. Uceta, Nacho Mas, Richard Hainsworth, Alex Schroeder, Bartosz Janus, Brad Gilbert, Jared Miller, Jason Cole, Jonathan Beebe, Patrick Sebastian Böker, Rafael Schipiura, Tzu-Li "tison" Chen, Tzu-Li Chen, sarna

If you would like to contribute or find out more information, visit,, ask on the mailing list, or ask on IRC #perl6 on freenode.

Additionally, we invite you to make a donation to The Perl Foundation to sponsor Perl 6 development: (put “Perl 6 Core Development Fund” in the ‘Purpose’ text field)

The next release of Rakudo (#128), is tentatively scheduled for 2018-11-17.

A list of the other planned release dates is available in the “docs/release_guide.pod” file.

The development team appreciates feedback! If you’re using Rakudo, do get back to us. Questions, comments, suggestions for improvements, cool discoveries, incredible hacks, or any other feedback – get in touch with us through (the above-mentioned) mailing list or IRC channel. Enjoy!

Please note that recent releases have known issues running on the JVM. We are working to get the JVM backend working again but do not yet have an estimated delivery date.

[^1]: See

[^2]: What’s the difference between the Rakudo compiler and the Rakudo Star distribution?

The Rakudo compiler is a compiler for the Perl 6 language. Not much more.

The Rakudo Star distribution is the Rakudo compiler plus a selection of useful Perl 6 modules, a module installer, Perl 6 introductory documentation, and other software that can be used with the Rakudo compiler to enhance its utility.