What's New in Perl v5.40?
![](/images/what-is-new-in-perl/what-is-new-in-perl.png)
This article was originally published at The Weekly Challenge.
Perl
, the most versatile and powerful programming language, continues to evolve. With the addition of Corinna to core Perl
, I look forward to every release for new features. On 9th June 2024
, we had the latest public release of Perl v5.40
. There have been significant enhancements in this release. You can check out the main attraction yourself.
In this post, I would like to share my personal favourites.
1. The new __CLASS__
keyword
2. The :reader
attribute for field variables
3. A space is permitted in the -M
command-line option
4. The new ^^
logical xor operator
5. The try/catch
feature is no longer experimental
6. for
iterating over multiple values at a time is no longer experimental
1. The new __CLASS__
keyword
Do you remember our good old friend, __PACKAGE__
? Well, it is a special token that returns the name of the package in which it occurs. Most commonly, you will find this __PACKAGE__->meta->make_immutable
in a Moose
class.
Similar to __PACKAGE__
, we now have a special token __CLASS__
for the new core OO
. In most cases, it would behave same as __PACKAGE__
. Having said that, it shines when you are dealing with subclass
.
use v5.40;
use experimental 'class';
class Example1 {
field $x = __CLASS__->default_x;
field $y = __CLASS__->default_y;
sub default_x { 10 }
sub default_y { 20 }
method sum { return $x + $y }
}
class Example2 :isa(Example1) {
sub default_x { 1 }
sub default_y { 2 }
}
say Example1->new->sum; # 30
say Example2->new->sum; # 3
2. The :reader
attribute for field variables
With the introduction of new OO
in Perl v5.38
, this is how one can create a class.
use v5.38;
use experimental 'class';
class Employee {
field $name :param;
field $age :param;
method name { return $name }
method get_age { return $age }
}
my $emp = Employee->new(name => "Joe", age => 40);
say $emp->name; # Joe
say $emp->get_age; # 40
If you noticed, the method name()
and get_age()
is just a generic getter
method.
Luckily in the latest release, the same can be achieved like below with the use of :reader
without having to explicitly define the getter
methods.
I must admit, it looks a lot cleaner definition of class comparatively.
use v5.40;
use experimental 'class';
class Employee {
field $name :param :reader;
field $age :param :reader(get_age);
}
my $emp = Employee->new(name => "Joe", age => 40);
say $emp->name; # Joe
say $emp->get_age; # 40
There are two variants, one that would give you regular getter and the second where you can provide your own method name.
You may be wondering, how about setter?
Well I am hoping in the next release we might get that too.
3. A space is permitted in the -M
command-line option
Prior to Perl v5.40
, this is how you would use -M
switch.
$ p538 -MList::Util=sum -E 'say sum(1, 2, 3, 4)'
10
However if you forced a space in an earlier Perl, you would get error Missing argument to -M
like below:
$ p538 -M List::Util=sum -E 'say sum(1, 2, 3, 4)'
Missing argument to -M
With the release of Perl v5.40
, you no longer get error.
$ p540 -M List::Util=sum -E 'say sum(1, 2, 3, 4)'
10
4. The new ^^
logical xor operator
Prior to Perl v5.40
, we had 3 low-precedence logical operators and
, or
and xor
. Also we had 2 medium-precedence logical operators &&
and ||
.
In the earlier release of Perl
, this is how one would use low-precedence xor
operator.
use v5.38;
my $x = 1;
my $y = 0;
($x xor $y) and say 'Either $x or $y is true but not both.';
With the addition of the new medium-precedence xor operator ^^
, the same can be achieved like below:
use v5.40;
my $x = 1;
my $y = 0;
$x ^^ $y and say 'Either $x or $y is true but not both.';
5. The try/catch
feature is no longer experimental
We all know try/catch
was added to the core Perl v5.34
as experimental.
use v5.34;
use experimental 'try';
try {
1/0;
} catch ($e) {
say "try/catch exception: $e";
}
It stayed experimental even in Perl v5.36
.
use v5.36;
use experimental 'try';
try {
1/0;
} catch ($e) {
say "try/catch exception: $e";
}
However it is no longer experimental in Perl v5.40
. Hurrah!!!
use v5.40;
try {
1/0;
} catch ($e) {
say "try/catch exception: $e";
}
6. for
iterating over multiple values at a time is no longer experimental
Do you remember iterating over multiple values at a time was an experimental feature added to the core Perl v5.36
?
use v5.36;
use experimental 'for_list';
for my ($p, $q) (1,2,3,4) {
say $p, $q;
}
It is no longer experimental in Perl v5.40
.
use v5.40;
for my ($p, $q) (1,2,3,4) {
say $p, $q;
}
Just to show realtime result, please see below:
$ p540 -E 'for my ($p, $q) (@ARGV) { say $p, $q; }' 1 2 3 4
12
34
$ p540 -E 'for my ($p, $q) (@ARGV) { say $p, $q; }' 1 2 3 4 5
12
34
5
$ p540 -E 'for my ($p, $q) (@ARGV) { say $p, $q; }' 1 2 3 4 5 6
12
34
56
I have only scratched the surface so far. Maybe in the next post I will try to explore further enhancements.
Tags
Mohammad Sajid Anwar
Mohammad is a 2022 White Camel Awardee and CPAN contributor. He enjoys submitting pull requests and speaking at Perl Conferences. He runs The Weekly Challenge. He is also co-editor of Perl Weekly newsletter. Find out more about him on his website.
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