Perl to Rust

by Ingy döt Net | | 4 min read

When Santa is doing his job in the Luxembourg area, I've always wondered how he gets from Perl to Rust.

Maybe he takes this route!

Welcome to Day 23 of the YAMLScript Advent Blog!

A couple of days ago we showed you how to use YAMLScript from Python.

One language binding down, forty-one to go!

Today we'll show you how to use YAMLScript with 3 new programming language bindings: Perl, Rust and Raku (aka Perl 6).

YAMLScript gets by with a little help from its friends:

These guys are awesome!

I Heard a Rumor!

Let's make up a little YAMLScript program that we can run from all the new YAMLScript bindings:

# hearsay.ys

# ys --load hearsay.ys | jq -r .


hackers =::
- ethiraric
- ingydotnet
- jjatria
- tony-o

languages =::
- Perl
- Python
- Raku
- Rust

=>: "I heard that @$rand-nth(hackers) uses YAMLScript
in their $rand-nth(languages) code!"

Now run (actually "load") this a few times using the YAMLScript ys --load command:

$ ys --load hearsay.ys | jq -r .
I heard that @tony-o uses YAMLScript in their Rust code!
$ ys --load hearsay.ys | jq -r .
I heard that @ethiraric uses YAMLScript in their Python code!
$ ys --load hearsay.ys | jq -r .
I heard that @jjatria uses YAMLScript in their Rust code!
$ ys --load hearsay.ys | jq -r .
I heard that @ingydotnet uses YAMLScript in their Perl code!
$ ys --load hearsay.ys | jq -r .
I heard that @vendethiel uses YAMLScript in their Raku code!

Works like a charm!

Now let's load this program from each of the new language bindings!


I've been programming Perl for a very long time. 25 years actually. I've published over 200 Perl modules on CPAN. My first one was called Inline::C which makes it trivial to write C bindings in Perl.

That's exactly what I needed to get done today to write this blog post about it. Ironically, I've forgotten how to use Inline::C, so I asked an AI to do it for me. It gave me something reasonable looking, but I couldn't get it working.

But the best part of Perl is its community! My good Perl friend Olaf told me to seek out a Perl programmer named JJ. I did and he was happy to help. He got it done in no time, and now I'm writing about it!!!

JJ used the newer Perl FFI binding framework called FFI::Platypus.

Let's use the new CPAN module YAMLScript to run our hearsay.ys program:

use v5.16.0;
use YAMLScript;
use Slurp;
my $program = slurp 'hearsay.ys';
say YAMLScript->new->load($program);
$ perl
I heard that @ethiraric uses YAMLScript in their Rust code!
$ perl
I heard that @ingydotnet uses YAMLScript in their Python code!

Just like the Python binding, the Perl module has a load method that takes a YAMLScript program as a string and returns the result as a Perl data structure.

Install YAMLScript with:

$ cpanm YAMLScript

Also like the Python binding, the Perl module (and all the other bindings) currently requires that you install yourself.

You can do this easily with:

$ curl | bash

Remember that this installs to /usr/local/lib by default, so you'll need to run this as root. (Or use the PREFIX option and set LD_LIBRARY_PATH yourself.)


@ethiraric is a Rust programmer who dropped by the YAML matrix chat a couple of weeks ago looking to improve Rust's YAML support. I told him about YAMLScript and suggested he write a Rust binding for it since it's just one FFI call.

He did and today we get to show it off.

Rust needs a bit more setup than Perl, but it's still pretty easy.

First run cargo new hearsay to create a new Rust project. Then edit hearsay/Cargo.toml to look like this:

name = "hearsay"
version = "0.1.0"
edition = "2021"
yamlscript = "0.1.2"

Then edit hearsay/src/ to look like this:

fn main() {
let input = std::fs::read_to_string("hearsay.ys").unwrap();
let output = yamlscript::load(&input).unwrap();

Now run cargo run and you should see something like this:

$ cargo run
Finished dev [unoptimized + debuginfo] target(s) in 0.01s
Running `target/debug/hearsay`
{"data":"I heard that @ethiraric uses YAMLScript in their Python code!"}

That's not quite right, but that's where things are at this moment. The load function is returning a JSON string, but it should be returning a Rust data structure for whatever was under the "data" JSON key. I'm sure @ethiraric will fix it soon!!!

It's actually fortunate that the Rust binding is not working yet, because it shows us how libyamlscript actually works.

The libyamlscript library currently has a single function that takes a YAMLScript string and returns a JSON string. Internally it compiles the YAMLScript to Clojure and evaluates the code using SCI. Then it converts the result to JSON and returns it. If the evaluation fails it returns JSON with all the error information under an "error" key. If successful, it returns JSON with all the result information under a "data" key.

The above call was successful, so that's why we see our expected result under the "data" key.


Raku is the new name for Perl 6. It's a completely different language than Perl 5, but it's still a lot like Perl.

@tony-o is a Raku programmer and my personal friend IRL for many years now. He really loves YAMLScript and wants to work on the language as a whole. Writing a Raku binding was a perfect way to get him started.

You can install the Raku binding with:

$ zef install YAMLScript

Here's the example Raku program:

use YAMLScript;
my $program = slurp 'hearsay.ys';
my YAMLScript $ys .= new;
say $ys.load($program);

Then you can run our hearsay program like this:

$ LD_LIBRARY_PATH=/usr/local/lib raku hearsay.raku
I heard that @tony-o uses YAMLScript in their Python code!

The Raku effort was a two person job. A big shout out to @vendethiel for helping @tony-o get the Raku binding working right.

Ven, as we call him, is someone I've known of and highly respected for many years. He was a major contributor to both CoffeeScript and Raku which have permanent places in my heart. He's Polyglot to the core and possibly more Acmeist than Ingy!

But my biggest thanks to Ven is for being my daily sounding board and protaganist for YAMLScript. He encourages my good ideas even when they are ambitious and crazy sounding. Every time he's disagreed with me, he's been right... Even if it sometimes takes me a while to see it.

Everyone in this penuiltimate advent blog post is a hero to me and definitely on Santa's nice list!!! (as far as I'm concerned)

Please do join me tomorrow for the final post of the YAMLScript Advent Blog 2023!