Perl 5.16 and beyond

Perl 5.16 and beyondJesse Vincentjesse@perl.org@obra

Recovering Perl 6Project Manager

Perl 5 Pumpking

Perl 5 Pumpking http://flic.kr/p/6StRmB

Perl 5 Pumpking

Whats a Pumpking?

I make decisions

(the unpopular ones)

I delegate

(any real work)

I document

(process and policy)

I destress

(other people)

I’m a manager

So, who makes Perl?

Many awesome people

I just stand around looking pretty...

...while other people do awesome stuff

Is your name in Perl’s AUTHORS ﬁle?

Are you aCPAN author?

You rock

You make Perl

The rules ofPerl Club

The REAL rules of Perl Club

commit e8cd7eae0498ecc1fd3801fe3160Author: Gurusamy Sarathy <gsar@cpan.org>Date: Sun Oct 10 23:48:07 1999 +0000add perlhack.pod from Nathan Torkington<gnat@frii.com>

That predates Damian’s talk

Yes, I know he’s capable of time travel

Rule 1

Larry is always right about howPerl should behave

Rule 2

Larry is allowed to change his mindabout any matter at a later date...

...regardless of whether he previouslyinvoked Rule 1

I’m not Larry

I’m nowhere near as clever

My shirts arenowhere near as loud

The rules aren’tjust for Larry

The rules aren’tjust for the Pumpking

The rules also apply to the Perl 5 core.

Rule 1

Perl is always right!

(TMTOWTDI)

Rule 2

The Perl 5 coreis allowed to...

change its mind?

Changing ourminds is easy

We are very good at it

Not ﬂailing wildly whenwe do has been hard

...and leads to problems

at least I haven’t heard this in a while...

Perl is Dead !

Perl is Dead !1!!

Perl is Dead !1!!one!

What I’ve beenhearing lately...

Where are we going?

It’s changing too fast.Can you slow down?

You made regexescrazier? /$#@!/l?

smartmatch isn’tnamed correctly...

we should call it psychoticmatch

Now that it’s undead,can we rename it?

I’ve been accused of lacking avision for Perl 5

What I lackis a ﬂame-proof suit http://en.wikipedia.org/wiki/File:Dance_Dance_Immolation.jpg

What I lack pe rl5 -po rt e rsis a ﬂame-proof suit http://en.wikipedia.org/wiki/File:Dance_Dance_Immolation.jpg

If I’d talked about myvision 2 years ago...

You would havelaughed at me

Improving Perl 5did not matter

We couldn’t evenput out a new release

In the past year...

Five StableReleases

A dozendevelopment releases

In metric, that’s1.2×10 1 releases

Perl 5.14.1 is thecurrent stablerelease of Perl 5

It came out in June

...as did Perl 5.12.4

..as did Perl 5.15.0

(all of them came out the same week)

It used to take us3 weeks to prepare a release

We made thePumpking do it

Now it takesless than a day

The 43 step process is documented

We have rotatingrelease engineers

Many of them arenew committers

Release engineersneed commit bits

Since the switch to git,we’ve nearly doubled our committer list

The worldhasn’t ended

Some of those releaseengineers have become proliﬁc contributors

Now thatreleasesare easy...

A Vision for Perl 5

New versions of Perl 5should not breakyour existing software

Old syntax and semantics must not stopPerl 5 from evolving

We need to be able to make mistakes as we rebuild Perl 5

We will make mistakesas we rebuild Perl 5

We have made mistakesas we’ve rebuilt Perl 5

We need to be able torecover from mistakes as we rebuild Perl 5

The runtime istoo big and must be slimmed down

Perl should havesane defaults

We need to be able to recover from lastyear’s “sane defaults”

It should be possible to build more of Perl 5 in Perl 5

Perl should runeverywhere

Rule 2:Perl is allowed to change its mind

That’s already true

That hurts programs and programmers

When your code runs, you have no ideawhat semantics it’ll see

use v5.14;

“Can I have a Perl that’s 5.14 or newer?”

“Anything newer than 5.14.0 would be great!”

“Ok. I’m 5.30. Have fun!”

That is not useful

It needs to change

From now on, declare the version of Perl 5 you expect

use v5.16;

“I want a Perl 5 thatworks like 5.16”

The runtime shouldhonor that request

Perl should give yousemantics as close aspossible to what you request

New featuresshould not workunder ‘use v5.$older;’

It’s critical that we be able to evolve

We need anescape hatch

We needRule 2

If you declare an old version, you get old syntax and semantics

...at least to thebest of our abilities

Perfection isnot possible

We can get far closer than we do now

Breaking existing code should be a last resort

In limitedcircumstances we will break backward compatibility

Some craziness can’t beﬁxed in an “optional” or lexical way

This is going to be hard work

A lot of hard work

It’s not impossible

Deprecation

Our currentdeprecation cycle is 1 year

“It warns in 5.16.0”

“It’s gone in 5.18.0”

That’s turning outto be too short

Very few operatingsystems release that frequently

Declare by default means we can makesome changes sooner

If it still works in old code, we get to change it with nodeprecation cycle

Some misfeaturesneed to come outlest they block major improvements

If we can’t emulate an old feature for oldcode, we get a longer deprecation cycle

“It dies in code thatdeclares ‘use v5.16’”

“It warns in older code on 5.16.0”

“It still warns in old code on 5.18.0”

“It’s gone in 5.20.0”

Rule 2 andOld Modules

We haven’t just beendeprecating and yanking broken old features

We’ve been doing thesame to old modules

They all end up on CPAN

This hurts users who wrote code with“no non-core deps”

We need to make iteasier to ship two ﬂavors of Perl 5

Hotel California

Last thing I remember, I wasRunning for the doorI had to find the passage backTo the place I was before’relax,’ said the night man,We are programmed to receive.You can checkout any time you like,But you can never leave!

aka Traditional Perl

The Times,TheyAre A-Changin’

The line it is drawnThe curse it is castThe slow one nowWill later be fastAs the present nowWill later be pastThe order is rapidly fadin’And the first one now will later be lastFor the times they are a-changin’

aka Bootstrappable Perl

There’s work going on to make this easier

Perl is a big language

There are bigger languages

Its harder to manage a big language

It’s harder to learn a big language

It’s harder to ﬁx bugs in a big language

We’re ok, but notamazing at corelanguage dev

As a community, we’reawesome at modules

How do we make Perla smaller language?

It’s possible to loadmodules that inject new builtins

It’s possible to loadmodules that inject old builtins

Time to start...

...refactoring

Lots of stuff in perl isnt necessarily part of Perl 5 the language

This stuff is part ofPerl 5 the chainsaw

I like our chainsaw

I’m not talking about deprecating this stuff

...just aboutdecoupling it

SysV IPC functions

Socket IO functions

Unix user & groupinformation functions

Unix networkinformation functions

Process and process group functions

Formats

smartmatch

...and probably a bunch of other stuff

If you don’t ‘use v5.16’,you’ll get whatever was in 5.14.

The implementation of SysV might be a module

As a Perl 5 user you won’t need to care

..and shouldn’t be able to tell

In the future we mightﬁx a bug or two in the modularized code

You could take the update withouthaving to upgrade all of Perl 5

Someday we mightremove things from the default runtime

Every feature weexternalize reclaimsprecious memory

Every feature weexternalize reclaims precious sanity

That just means you’ll need to declare youwant an older feature

...but only if you ask for v5.16

Existing codewon’t break

There are many, many unanswered questions

But it’s doable

I have proof!

Case study:Smartmatch

After YAPC::NA RJBS(and others) raised the issue of smartmatch

Perl has a history of borrowing from other languages

Perl has a history of thieving from other languages

We stolesmartmatchfrom Perl 6

It’s very clever

It’s nearlyimpossible to explain

It’s nearlyimpossible tounderstand

RJBS proposed a saner, much less clever, smart match

I don’t want to breakexisting code that uses “smartmatch”

Jesse Luehrs (DOY)was sitting in the back of my YAPC talk

All guys namedJesse are crazy

...threw himself at the problem

He extractedsmartmatch into an XS module

He reimplemented itentirely in pure perl

It’s slower, but it’sunderstandable and hackable

He implementedRicardo’s saner smartmatch as an alternative

I’m hoping that 5.16 ships DOY’s smartmatchimplementations

use v5.16; shouldload the new one in your scope

use v5.14; should load the old one in your scope

no “use v5.x;” line should load the old one in your scope.

We need a modulehierarchy for such things in core

The Test Suite

(Keeping us honest)

We have anamazing test suite

Over time, we need to tease apart (at least) 3 kinds of tests

Language tests

Bug-ﬁx tests

Implementation tests

To hold us to thecompatibility promises we make, we need a new test harness

“Run the test suites we shipped with allprevious releases...”

Weve been moving pretty fast

We’ve done some things I...

would notdo again

I’m going to be a lotmore skeptical about new features

...at least ones thatdon’t make it easier to have fewer features

We should havesane defaults

There’s lots of crazy in Perl 5

Syntactic Crazy

Semantic Crazy

Internal Crazy

Module Crazy

It may be time toconsider doing away with some of that

We’ve starteddown this road

“use v5.12” includes“use strict;”

Where do we go next?

warnings on by default

autodie-esque defaults

autodie does good for your code

using deep, scary evil

I will not show you the evil

Ask Paul Fenwick

You’re safe today. He’s not here

We should throwexceptions rather than just return on failure

I don’t want us to bikeshed anexception hierarchy

Heck, I’d be happy if westarted with dying with well-deﬁned strings

(I’d love an exception hierarchy)

2-arg open()gone by default

1-arg open()gone by default

No more package separator

Latin-1autopromote off by default

utf-8 everything by default

A clean, simplemeta-model with classesand methods

No indirect object syntax by default

But only if you declare “use v5.16”

Perl needs to becleaner, simpler and easier to work with

For users...

...and forimplementers

Perl should runeverywhere

Not just on everykind of hardware

Not just on everyOperating System

Every VM

Every Browser

Every Phone

Why isn’t Perl 5 onother runtimes?

“There’s no spec”

That didn’t stop Ruby

“Only Perl 5 can parse Perl 5”

That didnt stop PPI

To survive, a desperate hacker needs to be ableto reimplement Perl 5

Thanks!

How do we make this happen faster?

Perl 5 Maint Fund

perlfoundation.org

Questions/Tomatoes?http://blog.fsck.comjesse@perl.org@obra

So, you want to changethe name?

To something like Perl 7?

Or Raptor?

Our language is called Perl 5

Perl 6 is our precocious kid sister

I’m happy to talk about renaming Perl 5...

...if you write me asecond implementation

...that passes the test suite

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Perl 5.16 and beyond

by Jesse Vincent

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