Parrot

virtual machine for scripting languages

Development of Parrot

Parrot is related to Perl 6, but it is not Perl 6. To find out what it actually is, we need to know a little about how Perl works. When you feed your program into perl, it is first compiled into an internal representation, or bytecode; then this bytecode is fed to an almost separate subsystem inside perl to be interpreted. So there are two distinct phases of perl's operation -compilation to bytecode, and interpretation of bytecode. This is not unique to Perl; other languages following this design include Python, Ruby, Tcl and, believe it or not, even Java.

In previous versions of Perl, this arrangement has been pretty ad hoc: there hasn't been any overarching design to the interpreter or the compiler, and the interpreter has ended up being pretty reliant on certain features of the compiler. Nevertheless, the interpreter (some languages call it a Virtual Machine) can be thought of as a software CPU -the compiler produces "machine code" instructions for the virtual machine, which it then executes, much like a C compiler produces machine code to be run on a real CPU.

Perl 6 plans to separate out the design of the compiler and the interpreter. This is why we've come up with a subproject, which we've called Parrot, which has a certain, limited amount of independence from Perl 6. Parrot is destined to be the Perl 6 Virtual Machine, the software CPU on which we will run Perl 6 bytecode. We're working on Parrot before we work on the Perl 6 compiler because it's much easier to write a compiler once you've got a target to compile to!

The name "Parrot" was chosen after the 2001 April Fool's Joke which had Perl and Python collaborating on the next version of their interpreters. This is meant to reflect the idea that we'd eventually like other languages to use Parrot as their VM; in a sense, we'd like Parrot to become a "common language runtime" for dynamic languages.