Ryu - asynchronous stream building blocks


 #!/usr/bin/env perl
 use strict;
 use warnings;
 use Ryu qw($ryu);
 my ($lines) =
 print "Had $lines line(s) containing whitespace\n";


Provides data flow processing for asynchronous coding purposes. It's a bit like ReactiveX in concept. Where possible, it tries to provide a similar API. It is not a directly-compatible implementation, however.

For more information, start with Ryu::Source. That's where most of the useful parts are.

Why would I be using this?

Eventually some documentation pages might appear, but at the moment they're unlikely to exist.

As an expert software developer with a keen eye for useful code, you may already be bored of this documentation and on the verge of reaching for alternatives. The "SEE ALSO" section may speed you on your way.


Since RxPerl follows the ReactiveX conventions quite closely, we'd expect to have the ability to connect RxPerl observables to a Ryu::Source, and provide an adapter from a Ryu::Source to act as an RxPerl-style observable. This is not yet implemented, but may be added in a future version.

Most of the other modules in "SEE ALSO" are either not used widely enough or not a good semantic fit for a compatibility layer - but if you're interested in this, please ask about it or provide patches!



A source emits items. See Ryu::Source. If in doubt, this is likely to be the class that you wanted.

Items can be any scalar value - some examples:

  • a single byte

  • a character

  • a byte string

  • a character string

  • an object instance

  • an arrayref or hashref


A sink receives items. It's the counterpart to a source. See Ryu::Sink.


A stream is a thing with a source. See Ryu::Stream, which is likely to be something that does not yet have much documentation - in practice, the Ryu::Source implementation covers most use-cases.

So what does this module do?

Nothing. It's just a top-level loader for pulling in all the other components. You wanted Ryu::Source instead, or possibly Ryu::Buffer.

Some notes that might not relate to anything

With a single parameter, "from" and "to" will use the given instance as a Ryu::Source or Ryu::Sink respectively.

Multiple parameters are a shortcut for instantiating the given source or sink:

 my $stream = Ryu::Stream->from(
  file => 'somefile.bin'

is equivalent to

 my $stream = Ryu::Stream->from(
   file => 'somefile.bin'

Why the name?

  • $ryu lines up with typical 4-character indentation settings.

  • there's Rx for other languages, and this is based on the same ideas

  • 流 was too hard for me to type


Note that you're more likely to find useful methods in the following classes:


Instantiates a Ryu object, allowing "from", "just" and other methods.


Helper method which returns a Ryu::Source from a list of items.


Helper method which returns a single-item Ryu::Source.


Other modules

Some perl modules of relevance:

Other references

There are various documents, specifications and discussions relating to the concepts we use. Here's a few:


Tom Molesworth <> with contributions from:

  • Mohammad S Anwar

  • Michael Mueller

  • Zak Elep

  • Mohanad Zarzour

  • Nael Alolwani

  • Amin Marashi


Copyright Tom Molesworth 2011-2023. Licensed under the same terms as Perl itself.