Perl 5.16 and beyond

Perl 5.16 and beyond
Jesse Vincent
jesse@perl.org
@obra

Recovering Perl 6
Project Manager

Perl 5 Pumpking

http://flic.kr/p/6StRmB

I just stand around
looking pretty...

...while other people do
awesome stuff

Is your name in Perl’s
AUTHORS ﬁle?

The REAL rules of
Perl Club

commit e8cd7eae0498ecc1fd3801fe3160
Author: Gurusamy Sarathy <gsar@cpan.org>
Date: Sun Oct 10 23:48:07 1999 +0000

add perlhack.pod from Nathan Torkington
<gnat@frii.com>

That predates
Damian’s talk

Yes, I know he’s
capable of
time travel

Larry is always
right about how
Perl should behave

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

...regardless
of whether
he previously
invoked Rule 1

My shirts are
nowhere near
as loud

The rules aren’t
just for Larry

The rules aren’t
just for the Pumpking

The rules also apply
to the Perl 5 core.

The Perl 5 core
is allowed to...

Not ﬂailing wildly when
we do has been hard

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

What I’ve been
hearing lately...

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

You made regexes
crazier? /$#@!/l?

smartmatch isn’t
named correctly...

we should call it
psychoticmatch

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

I’ve been accused
of lacking a
vision for Perl 5

What I lack

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

What I lack
pe
rl5
-po
rt
e rs

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

If I’d talked about my
vision 2 years ago...

Improving Perl 5
did not matter

We couldn’t even
put out a new release

A dozen
development
releases

In metric, that’s
1.2×10 1 releases

Perl 5.14.1 is the
current stable
release of Perl 5

(all of them came out
the same week)

It used to take us
3 weeks to prepare
a release

The 43 step process is
documented

We have rotating
release engineers

Many of them are
new committers

Release engineers
need commit bits

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

Some of those release
engineers have become
proliﬁc contributors

New versions of Perl 5
should not break
your existing software

Old syntax and
semantics
must not stop
Perl 5 from evolving

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

We will
make mistakes

We have
made mistakes
as we’ve rebuilt Perl 5

recover from mistakes

The runtime is
too big and must be
slimmed down

Perl should have
sane defaults

recover from last
year’s “sane defaults”

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

Rule 2:
Perl is allowed to
change its mind

That hurts programs
and programmers

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

“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!”

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

“I want a Perl 5 that
works like 5.16”

The runtime should
honor that request

Perl should give you
semantics as close as
possible to what you
request

New features
should not work
under ‘use v5.$older;’

It’s critical that we be
able to evolve

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

...at least to the
best of our abilities

We can get far closer
than we do now

Breaking existing
code should be
a last resort

In limited
circumstances we will
break backward
compatibility

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

This is going to be
hard work

Our current
deprecation cycle
is 1 year

That’s turning out
to be too short

Very few operating
systems release that
frequently

Declare by default
means we can make
some changes sooner

If it still works in
old code, we get to
change it with no
deprecation cycle

Some misfeatures
need to come out
lest they block major
improvements

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

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

“It warns in older
code on 5.16.0”

“It still warns in old
code on 5.18.0”

We haven’t just been
deprecating and yanking
broken old features

We’ve been doing the
same to old modules

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

We need to make it
easier to ship two
ﬂavors of Perl 5

Last thing I remember, I was
Running for the door
I had to find the passage back
To 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!

The Times,They
Are A-Changin’

The line it is drawn
The curse it is cast
The slow one now
Will later be fast
As the present now
Will later be past
The order is rapidly fadin’
And the first one now will later be last
For the times they are a-changin’

There’s work going on
to make this easier

There are bigger
languages

It's 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 not
amazing at core
language dev

As a community, we’re
awesome at modules

How do we make Perl
a smaller language?

It’s possible to load
modules that inject
new builtins

It’s possible to load
modules that inject
old builtins

Lots of stuff in perl isn't
necessarily part of
Perl 5 the language

This stuff is part of
Perl 5 the chainsaw

I’m not talking about
deprecating this stuff

Unix user & group
information functions

Unix network
information functions

Process and process
group functions

...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 might
ﬁx a bug or two in the
modularized code

You could take the
update without
having to upgrade all of
Perl 5

Someday we might
remove things from the
default runtime

Every feature we
externalize reclaims
precious memory

Every feature we
externalize reclaims
precious sanity

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

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

...but only if you
ask for v5.18

...but only if you
ask for v5.20

There are many, many
unanswered
questions

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 stole
smartmatch
from Perl 6

It’s nearly
impossible to
explain

It’s nearly
impossible to
understand

RJBS proposed a saner,
much less clever,
smart match

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

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

All guys named
Jesse are crazy

...threw himself
at the problem

He extracted
smartmatch into
an XS module

He reimplemented it
entirely in pure perl

It’s slower, but it’s
understandable
and hackable

He implemented
Ricardo’s saner smart
match as an alternative

I’m hoping that
5.16 ships DOY’s
smartmatch
implementations

'use v5.16;' should
load 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 module
hierarchy for such
things in core

We have an
amazing
test suite

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

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

“Run the test suites
we shipped with all
previous releases...”

We've been moving
pretty fast

We’ve done some
things I...

I’m going to be a lot
more skeptical about
new features

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

There’s lots of crazy
in Perl 5

It may be time to
consider doing away
with some of that

We’ve started
down this road

“use v5.12”
includes
“use strict;”

autodie does good
for your code

I will not show
you the evil

You’re safe today.
He’s not here

We should throw
exceptions rather
than just return on
failure

I don’t want us to
bikeshed an
exception hierarchy

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

(I’d love an exception hierarchy)

No more ' package
separator

Latin-1
autopromote
off by default

utf-8 everything
by default

A clean, simple
meta-model
with classes
and methods

No indirect object
syntax by default

But only if you declare
“use v5.16”

“use v5.18”

“use v5.20”

Perl needs to be
cleaner, simpler
and easier
to work with

Not just on every
kind of hardware

Not just on every
Operating System

Why isn’t Perl 5 on
other runtimes?

“Only Perl 5 can
parse Perl 5”

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

How do we make this
happen faster?

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

So, you want
to change
the name?

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 a
second implementation

...that passes the
test suite

Perl 5.16 and beyond

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