perl 5.12 for everyday use

Perl 5.12for everyday use

Sunday, December 5, 2010

perl5100delta

5.12 isn’t like 5.10


perl5100delta


- after 5.8, we had to wait 5 years for 5.10


perl5100delta


- after 5.8, we had to wait 5 years for 5.10

- 5.12 came out 2 years after 5.10


perl5100delta

5.12 is a Nice Change


perl5100delta


- 5.10 was a huge set of changes


perl5100delta



- 5.12 is a lot smaller


perl5100delta




- 5.12 is not as compelling as 5.10


perl5100delta




- 5.12 is not as compelling as 5.10

- and that’s a good thing


perl5100delta

5.12 is a Mixed Bag


perl5100delta

5.12 is a Mixed Bag

- this talk isn’t just for beginners


perl5100delta

5.12 is a Mixed Bag


- some of these changes are at the edges


perl5100delta

5.12 is a Mixed Bag



- but they’re all practical


perl5100delta

5.12 is a Mixed Bag



- but they’re all practical

- except for the ones that aren’t


perl5132delta

By the way, 5.14...


perl5132delta

By the way, 5.14...

- is going to be awesome


perl5132delta

By the way, 5.14...


- and available in about nine months


perl5132delta

By the way, 5.14...


- and available in about nine months

- and it’s going to be awesome


perl5101delta

...and 5.10 is frozen.


perl5101delta


- 5.10 is the last release of the old way


perl5101delta



- that means it got some features backported


perl5101delta




- that will never happen again


perl5101delta




- that will never happen again

- I’ll point out 5.12isms that got into 5.10.1


but enough about other versions


let’s talk about 5.12


feature

First: A Warning


feature

First: A Warning

- 5.12 is backwards compatible


feature

First: A Warning


- but adds new keywords and operators


feature

First: A Warning



- they’re not enabled by default


feature

First: A Warning




- use feature ‘mtfnpy’;


feature

First: A Warning





- use 5.012;


feature

First: A Warning





- use 5.012;

- read the perldoc


feature

First: A Warning





- use 5.012;

- read the perldoc I’m a perldoc ref!


feature

First: A Warning





- use 5.012;

- read the perldoc


perlsyn

- the smart match operator changed

$old ~~ $new

also in 5.10.1


perldoc

~~

- no longer commutative; right side wins

- non-overloaded objects can’t be ~~ed

- still very complicated (23 behaviors)

- you won’t be using this every day


autodie

autodie

also in 5.10.1


autodie

autodie

- like Fatal

also in 5.10.1


autodie

autodie

- like Fatal

- but deadlier

also in 5.10.1


autodie

autodie

open my $fh, ‘>‘, $filename;

while (<$fh>) { ...}

close $fh;


autodie

autodie

open my $fh, ‘>‘, $filename or die “couldn’t open $filename: $!”;

while (<$fh>) { ...}

close $fh or die “couldn’t close $filename: $!”;


autodie

autodie

use autodie;

open my $fh, ‘<‘, $filename;

while (<$fh>) { ...}

close $fh;


autodie

autodie

use autodie;

open my $fh, ‘>‘, $filename;

while (<$fh>) { no autodie; rmdir or warn “couldn’t remove $_: $!”;}

close $fh;


perldoc

autodie problems

- autodie doesn’t affect print

- you must close filehandles explicitly


Unicode


perlunicode

Perl is Good at Unicode


perlunicode

Perl 5.12 is Better


perlunicode

Perl 5.12 is Better

- Unicode 5.2


perlunicode

Perl 5.12 is Better

- Unicode 5.2

- every character property is available


perlunicode

Perl 5.12 is Better

- Unicode 5.2

- every character property is available

- \X in regex is more sensible


perlunicode

“The Unicode Bug”


perlunicode


- strings aren’t always treated as Unicode


perlunicode



- this causes weird bugs that take ages to find


perlunicode



- this causes weird bugs that take ages to find

- use feature ‘unicode_strings’;


perldoc

use feature ‘unicode_strings’;


perldoc

use 5.12.0;


perldoc

use 5.10.0;


perldoc

use 5.10.0;

use feature qw( say state switch);


perldoc

use 5.12.0;


perldoc

use 5.12.0;

use feature qw( say state switch unicode_strings);


perldoc

use 5.12.0;

use feature qw( say state switch unicode_strings);

use strict;


Container Improvements


my %hash = (a => 1, b => 2);

while (my ($k, $v) = each %hash) { say “value for $k is $v”;}


my %hash = (a => 1, b => 2);

while (my ($k, $v) = each %hash) { say “value for $k is $v”;}

value for a is 1value for b is 2


my @array = qw(a b);



value for 0 is bvalue for 1 is a



for my $k (0 .. $#array) { say “value for $k is $array[$k]”;}




while (my ($k, $v) = each @array) { say “value for $k is $v”;}






for my $k (0 .. $#array) { say “value for $k is $array[$k]”;}


sub redump { my ($href) = @_; while (my ($k, $v) = each %hash) { say “value for $k is $v”; }}

my %hash = (a => 1, b => 2);

while (my ($k, $v) = each %hash) { print “== $k ==”; redump(\%hash);}



while (my ($k, $v) = each @array) { say “value for $k is $v”; do_something(\@array);}



while (my ($k, $v) = each @array) { my $string = $part_for_maybe_transient->bodyhandle->as_string; my $transient_pos = _match_position($string, $Not_An_Error); last unless defined $transient_pos; my $permanent_pos = _match_position($string, $Really_An_Error); my $orig_msg_pos = _match_position($string, $Returned_Message_Below); last if _position_before($permanent_pos, $orig_msg_pos); if (_position_before($transient_pos, $orig_msg_pos)) { say “value for $k is $v”; last if $message->effective_type eq ‘multipart/report’; last if !$first_part || $first_part->effective_type ne ‘text/plain’; my $string = $first_part->as_string; last if length($string) > 3000; # added return receipt (fix for bug #41870) last if $string !~ /auto.{0,20}reply|return receipt |vacation|(out|away|on holiday).*office/i; $self->log(“looks like an autoreply, ignoring.”); $self->{type} = “vacation autoreply”; $self->{is_bounce} = 0; return $self; }}


AVOIDeach @array


local ??


use Ancient::Utility qw(stuff);

my $result = do { local $Ancient::Utility::WIDTH = 10; stuff( $input );};


my $href = { a => 1, b => 2 };

my $result = do { local $href->{a} = 3; stuff( $href );};


my $href = { a => 1, b => 2 };

my $result = do { delete local $href->{a}; stuff( $href );};


$]


$[


perlvar

$[ - first index of array


perlvar


- so you can make $array[1] mean first


perlvar



- isn’t that awesome???


perlvar



- isn’t that awesome???

- yeah, about as awesome as Comic Sans


perlvar

$[

$[ = 1;

for (1 .. $#array) { ...}


perlvar

$[

for ($[ .. $#array) { ...}


perlvar

$[

Assigned to $[. Are you some kind of idiot or something? at -e line 123.


perlvar

$[

Use of assignment to $[ is deprecated at -e line 123.


More About Deprecations


@INC


perlvar

@INC: /usr/pkg/lib/perl5/5.8.0/i386-solaris /usr/pkg/lib/perl5/5.8.0 /usr/pkg/lib/perl5/site_perl/5.8.0/i386-solaris /usr/pkg/lib/perl5/site_perl/5.8.0 /usr/pkg/lib/perl5/site_perl /usr/pkg/lib/perl5/vendor_perl/5.8.0/i386-solaris /usr/pkg/lib/perl5/vendor_perl/5.8.0 /usr/pkg/lib/perl5/vendor_perl


perlvar

@INC: /usr/pkg/lib/perl5/site_perl/5.8.0/i386-solaris /usr/pkg/lib/perl5/site_perl/5.8.0 /usr/pkg/lib/perl5/site_perl /usr/pkg/lib/perl5/vendor_perl/5.8.0/i386-solaris /usr/pkg/lib/perl5/vendor_perl/5.8.0 /usr/pkg/lib/perl5/vendor_perl /usr/pkg/lib/perl5/5.8.0/i386-solaris /usr/pkg/lib/perl5/5.8.0


now we can remove stuff from the core distribution


Class::ISAPod::PlainerShell


Class::ISAPod::PlainerShellSwitch


… and …


my $x = get_input;


my $x = get_input;

if ( $x >= 0 ) {


my $x = get_input;

if ( $x >= 0 ) { do_something for 0 .. $x;


my $x = get_input;

if ( $x >= 0 ) { do_something for 0 .. $x;} else {


my $x = get_input;

if ( $x >= 0 ) { do_something for 0 .. $x;} else { ...


my $x = get_input;

if ( $x >= 0 ) { do_something for 0 .. $x;} else { ...}


my $x = get_input;

if ( $x >= 0 ) { do_something for 0 .. $x;} else { die “Unimplemented”}


sub virtual_method { ... }


sub method_I_will_write_later { ... }


Unimplemented at Some::Library line 123


AVOID...


AVOID...

(except maybe in slides and pseudocode)


sub virtual_method { confess ‘...’}

sub method_I_will_write_later { confess ‘...’}


error message improvements


perldiagSunday, December 5, 2010

perldiag

perl -MCGI -e’my $q = CGI->new;’Unrecognized character \xE2 in column 12 at -e line 1.


perldiag

perl -MCGI -e’my $q = CGI−->new;’Unrecognized character \xE2; marked by <-- HERE after y $q = CGI<-- HERE near column 12 at -e line 1.

perl -MCGI -e’my $q = CGI->new;’Unrecognized character \xE2 in column 12 at -e line 1.


perldiag

My Favorite 5.10-ism?

Use of uninitialized value $time in concatenation (.) or string at hello.plx line 9.

$str = “Greetings, $name. Your last login was $last. It is now $time.”;


perldiag


if (length $input->{new_email}) { $user->update_email(...);}


perldiag


Use of uninitialized value in length at - line 3120.



perldiag




overloading


my $object = Object->new;

print $object;


my $object = Object->new;

{ no overloading; print $object;}


my $filename = get_filename;

if (-d $filename) { handle_directory($filename);}


package Filename;

use overload ‘-X’ => sub { my ($self, $test) = @_; return $self->is_dir if $test eq ‘d’; return $self->cd_able if $test eq ‘x’; ...;};


my $file = get_file;

if (-d $file) { handle_directory($file);}


my $filename = get_file;

if (-d $file and -x _) { handle_directory($file);}


my $filename = get_filename;

if (-d -x $filename) { handle_directory($filename);}


AVOIDoverload -X


y2038


~$ perl5.10.0 -E ‘say scalar localtime 2**31-1’


~$ perl5.10.0 -E ‘say scalar localtime 2**31-1’Mon Jan 18 22:14:07 2038



~$ perl5.10.0 -E ‘say scalar localtime 2**31’



~$ perl5.10.0 -E ‘say scalar localtime 2**31’Fri Dec 13 15:45:52 1901


~$ perl5.12.0 -E ‘say scalar localtime 2**31-1’



~$ perl5.12.0 -E ‘say scalar localtime 2**31’



~$ perl5.12.0 -E ‘say scalar localtime 2**31’Mon Jan 18 22:14:08 2038


some non-everyday changes


A

B C

D

Method Resolution Order

mroSunday, December 5, 2010

A

B C

D


- 5.8 : D, B, A, C


A

B C

D


- 5.8 : D, B, A, C

- 5.10: D, B, C, A


A

B C

D


- 5.8 : D, B, A, C

- 5.10: D, B, C, A

- 5.12: Anything!


A

B C

D


- 5.8 : D, B, A, C

- 5.10: D, B, C, A

- 5.12: F

MRO::DefineSunday, December 5, 2010

use strict;use warnings;

package Booster::Gold;our $VERSION = ‘1.00’;

...

1;


use 5.12.0;use warnings;

package Booster::Gold 1.00;

...

1;


use 5.14.0;use warnings;

package Booster::Gold 1.00 { ...}

1;


http://www.perl.org/get.html


Any questions?


perl 5.12 for everyday use

Documents

autodie use autodie

new keywords

operators theyre

operators featuresunday

default featuresunday

talk isnt

old way perl5101deltasunday

feature mtfnpy featuresunday