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🦋 Rakudo – Raku on MoarVM, JVM, and JS

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This is Rakudo, a Raku Programming Language compiler for the MoarVM, JVM and Javascript virtual machines.

Rakudo is Copyright © 2008-2021, Yet Another Society. Rakudo is distributed under the terms of the Artistic License 2.0. For more details, see the full text of the license in the file LICENSE.

This directory contains only the Rakudo compiler itself; it does not contain any of the modules, documentation, or other items that would normally come with a full Raku distribution. If you're after more than just the bare compiler, please download the latest Rakudo Star package.

Rakudo is currently the most developed implementation of the Raku language; though there have been other partial implementations in the past. The

compiler has
backends. Note that each backend has a slightly different set of features. For historical compilers see

Recent changes and feature additions are documented in the

text file.

Building and Installing Rakudo

Build Status

See the
file for detailed prerequisites and build and installation instructions. Check
for platform specific notes.

The general process for building is running

with the desired configuration options (common options listed below), and then running
make install
. Optionally, you may run
make spectest
to test your build on Roast, the Official Raku test suite. To update the test suite, run
make spectest_update

Installation of Rakudo simply requires building and running

make install
. Note that this step is necessary for running Rakudo from outside the build directory. But don't worry, it installs locally by default, so you don't need any administrator privileges for carrying out this step.

Configuring Rakudo to run on MoarVM

To automatically download, build, and install a fresh MoarVM and NQP, run:

$ perl --gen-moar --gen-nqp --backends=moar

Please be aware, that this will install MoarVM and NQP into your given


Alternatively, feel free to git clone and manually and install them individually.

Configuration flags can be passed to MoarVM's
using the
flag. For example, if you wish to use Clang when GCC is the default compiler selected for your OS, use the
$ perl --gen-moar --moar-option='--compiler=clang' \
    --gen-nqp --backends=moar

If the compiler you want to use isn't known by MoarVM or you have multiple versions of the same compiler installed, the

flag can be used to pass its exact binary:
$ perl --gen-moar --moar-option='--cc=egcc' \
    --gen-nqp --backends=moar

Custom optimization and debugging levels may also be passed through:

$ perl --gen-moar --moar-option='--optimize=0 --debug=3' \
    --gen-nqp --backends=moar

For more information on how MoarVM can be configured, view MoarVM's

Configuring Rakudo to run on the JVM

Note that to run Rakudo on JVM, JDK 1.9 or higher must be installed. To automatically download, build, and install a fresh NQP, run:

$ perl --gen-nqp --backends=jvm

If you get a

java.lang.OutOfMemoryError: Java heap space
error building rakudo on the JVM, you may need to modify your NQP runner to limit memory use. e.g. edit the nqp-j / nqp-j.bat executable (found wherever you installed to, or in the
directory) to include
-Xms500m -Xmx3g
as options passed to java. Alternatively, you can set
env var; e.g.
export JAVA_OPTS="-Xmx51200000000"

Please be aware, that this will install NQP into your given


Alternatively, feel free to git clone manually and install it individually.

Multiple backends at the same time

By supplying combinations of backends to the

flag, you can get two or three backends built in the same prefix. The first backend you supply in the list is the one that gets the
name as a symlink, and all backends are installed separately as
for Rakudo on MoarVM, or JVM respectively.

The format for the

flag is:
$ perl --backends=moar,jvm --gen-moar --relocatable
$ perl --backends=ALL --gen-moar --relocatable

refers to


Ensure the test suite is installed

The roast test suite is installed as the

directory under your rakudo directory. If your installed rakudo source directory doesn't have
installed, then you can clone it like this:
git clone t/spec

Note the rakudo code includes an entry in its

file so git will ignore any content under

Now you can run tests in the rakudo directory.

Running tests

Run the full spectest:

$ make spectest   # <== takes a LONG time!!

To run a single test, one must use

because of the tooling required to run the spectests. For example:
$ make t/spec/S03-operators/comparison.t

Run all tests in one S* directory with a sh script. One example:

$ cat

specify the desired directory:


collect the individual files

F=$(ls $D/*t)

and run them

for f in $F do echo "Testing file '$f'" make $f done echo "All tests in dir '$D' have been run."

That can be written as a one-liner:

for f in $(ls t/spec/S26-documentation/*t); do make "$f"; done

Where to get help or answers to questions

There are several mailing lists, IRC channels, and wikis available with help for the Raku Programming Language and Rakudo. Figuring out the right one to use is often the biggest battle. Here are some rough guidelines:

The central hub for Raku information is This is always a good starting point.

If you have a question about Raku syntax or the right way to approach a problem using Raku, you probably want the “[email protected]” mailing list or the IRC channel. The mailing list is primarily for the people who want to use Raku to write programs, so newbie questions are welcomed there. Newbie questions are also welcome on the #raku channel; the Rakudo development teams tend to hang out there and are generally glad to help. You can follow @raku_news and on Twitter, there's a Raku news aggregator at Planet Raku.

Questions about NQP can also be posted to the #raku IRC channel. For questions about MoarVM, you can join #moarvm on freenode.

Code of Conduct

The Raku community is committed to providing a welcoming, inclusive, safe, and enjoyable environment for everyone. Programming should be

. The Raku Community therefore has adopted a Code of Conduct. Please see the CoC Incident Report Guide should you feel the need to report any violations of the Code of Conduct.

Reporting bugs


Submitting patches

If you have a patch that fixes a bug or adds a new feature, please create a pull request using github's pull request infrastructure.

See our contribution guidelines for more information.

Line editing and tab completion

If you would like simple history and tab completion in the

executable, you need to install the Linenoise module. The recommended way to install Linenoise is via zef:
$ zef install Linenoise

An alternative is to use a third-party program such as rlwrap. Documentation on rlwrap can be found here.


See CREDITS for the many people that have contributed to the development of the Rakudo compiler, some of which have left this existence way too early.

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