Gerard Goossen talks about Kurila, a Perl 5 fork

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A few days ago Gerard Goossen released version 1.5 of his kurila project to the CPAN, a fork of Perl 5, both the language and the implementation. I talked with about the history of this new direction.


Andy: Why Kurila? Who would want to use it? What are your goals?

Gerard: Kurila is a fork of Perl 5. Perl Kurila is a dialect of Perl. Kurila is currently unstable, the language is continuously changing, and has just started.

There are a few goals, not all of them going in the same direction. One of the goals is to simplify the Perl internals to make hacking on it easier. Another is to make the Perl syntax more consistent, remove some of the oddities, most of them historical legacy.

What is currently being done is removing some of the more object/error-prone syntax like indirect-object-syntax and removing symbol references. Both of these are not yet very radical yet, most modern Perl doesn't use indirect-object-syntax or symbol references.

But I am now at the stage of doing more radical changes, like not doing the sigil-change, so that my %foo; $foo{bar} would become my %foo; %foo{bar} .

Andy: Where do you see Kurila getting used? Who's the target audience for it?

Gerard: Kurila would be used for anything where currently Perl is being used. I am using Perl for large websites so changes will be favored in that direction.

I am working for TTY Internet Solutions, a web development company. We develop and maintain websites in Perl, Ruby and Java. Websites we develop include www.2dehands.be, www.sellaband.com, www.ingcard.nl and www.nationalevacaturebank.nl. Of these www.2dehands.be and www.nationalevacaturebank.nl are entirely written in Perl.

We are not yet using kurila in production, but I have a testing environment of www.2dehands.nl which is running on Kurila. Developing Kurila is part of my work at TTY.

Many of the changes in Kurila are inspired by bugs/mistakes we made developing these sites. It started with the UTF8 flag. We encountered many problems making our websites UTF-8 compatible. In many cases the UTF8-flag got "lost" somewhere, and after combining it with another string, the string got internally upgraded and our good UTF-8 destroyed. Because everything we have is default UTF-8. The idea was simply to make UTF-8 the default encoding, instead of the current default of latin1.

Andy: Did you raise the possibility of changing the default encoding in Perl?

Gerard: The problem is that changing the default encoding the UTF-8 is that is destroys the identity between bytes and codepoints. So it's not a possibility for Perl 5. Like what does chr(255) do? Does it create a byte with value 255 or character with codepoint 255?

I made a patch removing the UTF-8 flag and changing the default encoding to UTF-8 and sent it to p5p.

Andy: What was the response?

Gerard: There was as good as no response to it, I guess because it was obvious that it seriously broke backwards compatibility and the patch was quite big, making it difficult to understand.

About two weeks after the utf8 patch, I announced that I wanted to change the current Perl 5 development to make it a language which evolves to experiment with new ideas, try new syntax and not be held back by old failed experiments. One of the interesting things about Perl is that it has a lot of different ideas and these are coupled to the syntax.

There was of course the question of why not Perl 6.  That it should/could be done in backwards-compatible way. That there is no way of making the Perl internals clean, that is better to start over.

And about half a year ago I announced that I had started Kurila, my proof of-concent for the development of Perl 7. Rewriting some software from scratch is much more difficult then it seems, and I think starting with a well proven good working base is much easier. Perl 5 is there, it is working very good, has few bugs, etc., but it can be much better if you don't have to worry about possibly breaking someone code, and just fix those oddities.

Andy: Do you have a website for it?  Are you looking for help?

Gerard: There isn't a website yet, and also no specific mailing list, currently all the discussion is on p5p. There is a public git repository at git://dev.tty.nl/perl.

Andy: What can someone do if he/she is interested in helping?

Gerard: Contact me at gerard at tty dot nl. Make a clone of git://dev.tty.nl/perl and start making changes.

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