Perl 5.28 introduces several new features including auto referencing of subroutine arguments, fancier signatures that allow type constraints, distributed map and grep functions to parallelize work, an upgraded safe module, three-state test outcomes in TAP, close enough comparators, new array manipulation operators, upgradable assignment with =^, better support for Git conflicts, and improved diagnostics.

1. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Perl 5.28
New Features
www.perl.org
Alpine Perl Workshop 2016 • brian d foy

2. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Auto referencing
use feature qw(auto_ref);
no warnings qw(experimental::autoref);
foo( %hash, @array );
sub foo ( %hash, @array ) {
…
}

3. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Fancier signatures
use feature qw(signatures);
no warnings qw(experimental::signatures);
sub foo ( $date[DateTime] ) { … }
sub bar ( $n[Int]/Rat/ ) { … }
sub baz ( $n[+&bar] ) { … }
sub quux ( $[+&bar|Int] ) { … }

4. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Distributed map / grep
use feature qw(parallel);
no warnings qw(experimental::parallel);
@{^PERL_WORKER_POOL} = ‘192.168.1/8’;
my @transformed = map { foo() } @array;
sub foo :distributive { … }

5. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Better Safe
use feature qw(safe);
no warnings qw(experimental::safe);
use safe qw(:all);
no safe qw(regex networking);
m/…/; # dies at compile time
{ # new READONLY ${^PERL_LEVEL}
no safe qw(:level1);
…
}

6. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Three-state TAP
ok 1 - 2 + 2 = 4
ok 2 - 2 - 2 = 0
not 3 - 2 + 2 = 5
meh 4 - documentation is correct
ok 5 - Another test passed

7. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Close enough comparators
7 =? 8 # True
7 !=? 9 # False
7 >+ 6 # False
7 >+ 3 # True
7 >++ 3 # False
7 <+ 9 # False
7 <+ 14 # True
7 <++ 14 # False

8. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
New array operators
unshift @array, 6; # ( 6 )
push @array, 2; # ( 6, 2 )
shove @array, 4; # ( 6, 4, 2)
cutin @array, 5; # ( 6, 5, 4, 2 )
vip @array, 7; # ( 6, 3, 4, 2 )

9. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Upgradable =
my $scalar =^ ( 1,, 2,, 3,, 4,, );
say $scalar; # fatal, no $scalar
say “@scalar”; # 1 2 3 4
my @array =^ ( cat >=> Buster ); # %array
use feature qw(upgrade_assign);

10. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Yada Yada Alotta
use feature qw(alotta);
no warnings qw(experimental::alotta);
while (<>) {
…
}

11. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Better Git Interop
•Compiler recognizes conflict markers
•Will run both versions
•Chooses version with right answer

12. ThePerlReview•www.theperlreview.com
Perlv5.28NewFeatures
Better Diagnostics
•“(W+) Warnings turned off in lexical scope,
but this warning is really important.”
•“(P) Converting code into another way to
do it. Ways to do counter is 3 (2 to go).”
•“(I) Nope. Just, nope.”
•“(0) This program appears to be a waste of
time. Exiting.”