What's new in Perl 5.10?

What is new in Perl 5.10?
Paul Fenwick
Audrey Tang
Leon Brocard

slidehist
Monday: I'm presenting?
Tuesday: download Paul's slides
Wednesday: tweak design
Thursday: play with fonts
Friday: argh slides on a plane
Saturday: release!

perlhist
1987: 1.0
1988: 2.0
1989: 3.0...
1991: 4.0...
1994: 5.0

perlhist 5.0
1994: 5.0
1995: 5.1
1996: 5.2, 5.3
1997: 5.4
1998: 5.5...
2000: 5.6...
2002: 5.8

5.8 perlhist
2002: 5.8.0
2003: 5.8.1, 5.8.2
2o04: 5.8.3, 5.8.4, 5.8.5, 5.8.6
2005: 5.8.7
2006: 5.8.8

2007
Stable: 5.8.9
New: 5.10
New new: 6.0.0

New features
Perl 5.10 has new features
Sorry Sebastian

New?
new lexically-scoped feature pragma:
use feature qw(say switch);
use feature qw(:5.10);
use 5.10;

Optimise programmer time
Most advanced programming language ever!
Perl: print “hello ”
Perl 6: say “hello”
Perl 5.10: say “hello”

Save typing
My poor fingers!
Also none of this nasty quoting business
This might seem like it's trivial...

Or
$c = $a | | $b is handy
confused by empty string, undef or zero

Defined or
$c = $a // $b is handier
same as $c = defined($a) ? $a : $b

dor and err
There's also low-precedence //
use feature qw(dor err);
fileno($x) dor die 'That's not a filehandle';
fileno($x) err die 'That's not a filehandle';

State variables
The old way of having a persistent variable:
{ my $i = 0; sub incrementor { return $i++; } }

State variables
use feature 'state'; sub incrementor { state $i = 0; return $i++; }

Local caches
State variables can live deep inside subroutines...
for my $x (...) { for my $y (...) { state %seen; next if $seen{$x}{$y}++; } }

Switch
Perl 5.10 introduces a native switch statement.
Similar to Perl 6's switch, and Switch.pm (source filter)
Built into the Perl interpreter

Guessing Game
use feature qw(switch say); my @guessed; my $num = int(rand 100)+1; while (my $guess = <STDIN>) { chomp $guess; given($guess) { when (/D/) { say "Give me an integer" } when (@guessed) { say "You've tried that" } when ($num) { say "Just right!"; last } when ($_ < $num) { say "Too low"; continue } when ($_ > $num) { say "Too high"; continue } push(@guessed,$_); } }

foreach / when
use feature 'switch'; foreach (@cool_things) { when (/pirate/) { $pirate++ } when (/ninja/) { $ninja++ } when (/robot/) { $robot++ } say "$_ doesn't look cool..."; }
when automatically calls next at the end of its block

Smart-match
use feature '~~'; if ($x ~~ @array) { say "$x exists" } if ($x ~~ /ninja/) { say "Ninja in string"} if (@x ~~ /ninja/) { say "Ninja in array" } if ($key ~~ %hash) { say "$key exists" } if ($subref ~~ $arg) { say 'sub($arg) true' }

Smart-match
use feature '~~'; if (@array ~~ $x) { say "$x exists" } if (/ninja/ ~~ $x) { say "Ninja in string"} if (/ninja/ ~~ @x) { say "Ninja in array" } if (%hash ~~ $key) { say "$key exists" } if ($arg ~~ $subref) { say 'sub($arg) true' }
~~ can be overloaded

UNIVERSAL::DOES
Traditionally isa would be used to determine the capabilities of a class:
provides a way to show compatibility, without inheritance
$obj‐>isa('Logger');
$obj‐>DOES('Logger');

Helicopter
package Helicopter; sub DOES { my ($this, $interface) = @_; return 1 if ($interface eq "Airplane"); return $this->SUPER::does($interface); }

Constant (un-)folding
Perl 'folds' constants at compile time
9+5 gets converted to 14
In Perl 5.10, exceptional constants are unfolded
They'll still throw run-time exceptions if you try to execute them

Hash::Util::FieldHash
5.10 comes with support for Field Hashes, which:
Can use references as hash keys
Reference-keys migrate correctly across threads
Entries to stale references are automatically deleted
(Inside-Out objects work nicely)

Assertions
Perl 5.10 implements real assertions
Normally compiled away
Can be enabled on a per-module basis
# This is normally compiled away sub assert_sanity :assertion {...} # Enable assertions for MyModule perl -A=MyModule prog.pl

User-defined lexical pragmata
We've used lexical pragmata for years: { use strict; ... }
In Perl 5.10 you can write your own!
%^H allows "hints" to be attached to the optree
use feature is implemented this way

More modules
encoding::warnings
Math::BigInt::FastCalc
Time::Piece
Win32API::File
CPANPLUS

CPANPLUS
Hi Jos!
It's about time, isn't it?
Means we have many other modules in the core...

Regex engine
perlreguts
No longer recursive
Single char char-classes treated as literals
Trie optimisation of literal string alternations /foam|foal|foad/ => /foa[mld]/
Aho-Corasick start-point optimisation
Regex engine
Pluggable: use re::engine::PCRE;
Named capture buffers
/$(?<price>d+)/ ... $+{price}
More

Other goodies
Misc Attribute Decoration
$AUTOLOAD can be tainted
Source filters in @INC
encodings::warnings is lexical
Better threads
Faster UTF-8

More other goodies
Faster stat() on Windows
Relocatable installs
Overloading for re-blessed objects
Better Windows support
Smaller memory footprint (slightly faster)
More documentation

More details?
http://search.cpan.org/dist/perl/pod/perl594delta.pod

Questions?

When will it be out?
Stable: 5.8.9 “by April 1st”
New: 5.10 “after lunch, before Christmas”
New new: 6.0.0 “after lunch, before Christmas”

Any other questions?

License
These slides are Copyright 2006 Paul Fenwick, Audrey Tang, Leon Brocard
The text may be distributed under your choice of any of the following:
The license terms of Perl itself
GNU Free Documentation License
Creative Commons Attribution ShareAlike

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What's new in Perl 5.10?

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