This document summarizes some new features in Perl 5.26, including: - Scalar hashes now return the number of keys instead of "hash statistics" - POSIX::tmpnam is deprecated and replaced by File::Temp for creating temporary files - All opening braces ('{') in regular expressions are now special instead of literal - The /xx flag can now be used multiple times and applies regex rules inside character classes - Heredoc syntax now allows indentation of content without affecting output - The '.' directory is no longer implicitly included in @INC for security reasons - A new @{^CAPTURE} array provides access to matched regular expression captures

1. Perl v5.26
New
Features
AmsterdamX.pm, 8 Jun 2017
Tunisian Camels (2010), from Ray on Flickr

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Perlv5.26NewFeatures
scalar %hash

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Perlv5.26NewFeatures
The key count
• A hash in scalar context returned “hash
statistics”
my %h = (a=>1, b=>2);
say scalar %h; # ‘2/8’
• Everyone expected it to be the number of keys
• Now that’s what they get.
my %h = (a=>1, b=>2);
say scalar %h; # 2

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Perlv5.26NewFeatures
POSIX::tmpnam

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Perlv5.26NewFeatures
use File::Temp qw/ tempfile tempdir /;
$fh = tempfile();
($fh, $filename) = tempfile();
($fh, $filename) = tempfile(
$template, DIR => $dir);
($fh, $filename) = tempfile(
$template, SUFFIX => '.dat');
($fh, $filename) = tempfile(
$template, TMPDIR => 1 );

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Perlv5.26NewFeatures
{

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Regexes are messier
• N{NAME}, x{ABCD}, p{PROPERTY},
P{PROPERTY}, b{…}, B{…}, a{MIN,MAX},
and so on
• New things are probably on the way
• So, every { is now special and not literal
• Some old tools might break

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Perlv5.26NewFeatures
/xx

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More Meaninglessness
• /x makes most whitespace in a regex
insignificant
• And, you can add comments inside regex
• Except in a character class [ a b c ]
• Or [ a #comment b c ]
• Previously, Perl ignored additional /x
• Maybe you added /xxx to honor Amsterdam.
• Now you can’t.
• /xx now applies the rules inside a char class

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Perlv5.26NewFeatures
Apple Part Number
my $string = ' Z007LL/A';
my $pattern = qr/
A
# M = First sale, F = Refurbished, P = Personalized
[ M F P ]
# probably not all these letters here
[ A-Z ]
d+
(?: # country codes
LL |
[ FBEJTXYC ]
)
/
[ A B C ] # revision
z
/xx;
say $string =~ $pattern ? 'Matched' : 'Missed';

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Perlv5.26NewFeatures
Hopes for /xxx
(?:L [
A # Colombia, Ecuador, El Salvador, … Peru
E # Argentina
L # US
Z # Chile, Paraguay, Uruguay
]
|
[
F # France
B # Ireland, UK
E # Mexico
J # Japan
T # Italy
X # Australia, New Zealand
Y # Spain
C # Canada
]
)

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Perlv5.26NewFeatures
Indented Heredocs

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Perlv5.26NewFeatures
my $string = <<~“HERE";
This is the first line
This is the second line
HERE
This is the first line
This is the second line

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Perlv5.26NewFeatures
my $string = <<~“HERE";
This is the first line
This is the second line
HERE
This is the first line
This is the second line

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Perlv5.26NewFeatures
No . in @INC

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Perlv5.26NewFeatures
More Securitiness
• What’s that . anyway?
• This doesn’t mean that you are safe
• CPAN tested, but not DarkPAN tested
• do warns when it fails to load a file from .
• You can disable this, but I won’t tell you how

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@{^CAPTURE}

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List of Captures
• %{^CAPTURE} is %+ (named captures)
• %{^CAPTURE_ALL} is %- (all named captures)
• @{^CAPTURE} is the cool one.
• ${^CAPTURE}[INDEX] is the numbered capture
minus 1

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Perlv5.26NewFeatures
sub match_it_1 ( $rx, $string ) {
$string =~ $rx;
say "$1•$2•$3"; # Hoping there's three
}
sub match_it_2 ( $rx, $string ) {
$string =~ $rx;
say join '•', map {
substr $string, $-[$_], $+[$_]-$-[$_]
} 1 .. $#-;
}
sub match_it_3 ( $rx, $string ) {
$string =~ $rx;
local $" = '•';
say "@{^CAPTURE}";
}

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Perlv5.26NewFeatures
Questions