This document discusses the history and features of recent Perl releases. It describes changes such as new features like smart matching, performance enhancements, deprecated functionality and removals, updated modules, documentation improvements, and bug fixes between Perl 5.8 through 5.20. Key details include added features like given/when blocks, improvements to regular expressions, addition of new modules, and transition from Perforce to Git for version control.

1. Perl .
Léon Brocard
London Perl Workshop

2. Me
Léon Brocard
French, live in London
Like food
Like the colour orange
Founded Amsterdam.pm, Bath.pm, Croydon.pm
Now leader of London.pm
Started YAPC::Europe
perl hacker

3. Releases
- - Perl
- - Perl
- - Perl
- - Perl
- - Perl
...
Perl is years old
Perl is years old

4. Perl releases
- - Perl
- - Perl .
- - Perl .
- - Perl .
- - Perl .
- - Perl .
- - Perl . .
- - Perl . .
- - Perl . .
- - Perl . .

5. Perl . New features

6. Perl . New feature
use feature ’say’;
use feature ’state’;
use feature ’switch’;
...
use feature ’:5.10’;

7. Say operator
Just like print, but implicitly appends a newline
use feature ’say’;
say ’Hello!’;

8. State operator
Persistent private variables
use feature ’state’;
sub gimme_another { state $x; return ++$x }

9. Smart match operator
$a ~~ /foo/
@a ~~ /foo/
$a ~~ @b
$a ~~ %b
...

10. Switch and smart match operator
use feature ’switch’;
given ($foo) {
when (/^abc/) { $abc = 1; }
when (/^def/) { $def = 1; }
when (/^xyz/) { $xyz = 1; }
default { $nothing = 1; }
}

11. Switch and smart match operator
use feature ":5.10";
given($foo) {
when (undef) { say ’$foo is undefined’; }
when ("foo") {
say ’$foo is the string "foo"’;
}
when ([1,3,5,7,9]) {
say ’$foo is an odd digit’;
continue; # Fall through
}
when ($_ < 100) { say ’< 100’; }
when (&complicated_check) {
say ’a complicated check for $foo is true’;
}
default { die ’Eeeeek’; }
}

12. De ned-or operator
$a // $b
defined $a ? $a : $b
$c //= $d;
$c = $d unless defined $c;

13. Regular expressions
Recursive patterns
Named capture bu ers
Possessive quanti ers
Backtracking control verbs
Relative backreferences
Vertical and horizontal whitespace, and linebreak

14. Named capture bu ers
use feature ’say’;
my $time = ’Time: 01:02:03’;
if ($time =~ /Time:s(d+):(d+):(d+)/) {
say "$1 / $2 / $3";
}
if ($time =~ /Time:s(?<hours>d+):
(?<minutes>d+):(?<seconds>d+)/x) {
say "$+{hours} / $+{minutes} / $+{seconds}";
}

15. New modules
Archive::Extract, Archive::Tar,
Compress::Zlib, CPANPLUS, Digest::SHA,
encoding::warnings, ExtUtils::CBuilder,
ExtUtils::ParseXS, File::Fetch,
Hash::Util::FieldHash, IO::Zlib, IPC::Cmd,
Locale::Maketext::Simple, Log::Message,
Log::Message::Simple, Math::BigInt::FastCalc,
Module::Build, Module::CoreList, Module::Load,
Module::Load::Conditional, Module::Loaded,
Module::Pluggable, Object::Accessor,
Package::Constants, Params::Check,
Pod::Escapes, Pod::Simple, Term::UI,
Time::Piece, Win32API::File.

16. New documentation
perlpragma — How to write a user pragma
perlglossary — Perl Glossary
perlreguts — Regular expression engine internals
perlreapi — Regular expression plugin interface
perlunitut — Perl Unicode Tutorial
perlunifaq — Perl Unicode FAQ
perlcommunity — Overview of the Perl community
CORE — Pseudo-namespace for Perl’s core routines

17. Performance enhancements
In-place sorting
Lexical array access
XS-assisted SWASHGET
Constant subroutines
PERL_DONT_CREATE_GVSV
Weak references are cheaper
sort() enhancements
Memory optimisations
UTF- cache optimisation
Sloppy stat on Windows
Regular expressions optimisations

18. Deprecations
Pseudo-hashes have been removed
Removal of the bytecode compiler and of perlcc
Removal of the JPL

19. Other
Lexical $_, _ prototype, UNITCHECK blocks, mro pragma,
readpipe() is now overridable, default argument for
readline(), UNIVERSAL::DOES(), formats, byte-order
modi ers for pack() and unpack(), no VERSION,
chdir, chmod, chown on lehandles, OS groups, recursive
sort subs, exceptions in constant folding, source lters in @INC,
new internal variables, UCD . . , Miscellaneous Attribute
Decoration, con guration improvements, compilation
improvements, relocatable installations, nicer internals
bison-based parser . . .

20. Perl . .
Many bug xes: @_
Optimised internals: isa()

21. New features, modules
DTrace support
autodie
Compress::Raw::Bzip
parent
Parse::CPAN::Meta

22. Platform updates
AIX
Cygwin
FreeBSD
Irix
Haiku
MirOS BSD
NetBSD
Stratus VOS
Symbian
Win
VMS

23. Feature tweaks
given/when
switch
smart match

24. Deprecations
Switch
suidperl

25. Internal changes
Moved from Perforce to Git
Changed directory structure

26. Better quotes
e J.R.R. Tolkien quotes at the head of each C source
le have been checked and proper citations added

27. More tests
Perl . , core tests
(+ , more for bundled libraries)
Perl . . , core tests
(+ , more for bundled libraries)
Perl . . , core tests
(+ , more for bundled libraries)

28. Recent past and future
Perl . . : Léon Brocard on Nov ,
Perl . . : Jesse Vincent on Dec ,
Perl . . : Ricardo Signes on Jan ,
Perl . . : Steve Hay on Feb ,
Perl . . : Ask Bjørn Hansen on Mar ,
...
Perl . : Jesse Vincent early

29. Use Perl . now!
Perl . is faster
Perl . uses less memory
Perl . has more features
Perl . is backwards compatible