Perl::...Newline(3pm)

💅 Perl::...Newline(3pm) 💅

okay bestie, welcome to another episode of User Contributed Perl Documentation, and today's main character is Perl::...Newline(3pm) — the page about keeping your fat comma glued to its quoted word. no cap, this one's a bop. 🎀

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✨ NAME ✨

Perl::Critic::Policy::CodeLayout::ProhibitFatCommaNewline — keep a fat comma on the same line as its quoted word 🫶

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🌸 DESCRIPTION 🌸

so this policy lives inside the Perl::Critic::Pulp add-on, right, and what it does is it snitches on you when there's a newline chilling between a fat comma and the bareword in front of it. for Perl builtins, it's giving 🚨:

my %h = (caller         # bad, builtin called as a function
         => 'abc');

and for all words when you're targeting Perl 5.6 and earlier 🦋:

use 5.006;
my %h = (foo            # bad, all words in perl 5.6 and earlier
         => 'def');

why do we care, you ask? because when there's a newline between the word and the fat comma like that, the word executes as a function call — builtins always do this, and user-defined ones do it in Perl 5.6 and earlier too — so you get its return value instead of a word string. it's giving chaos energy honestly 😭

and that return value is probably not what you intended, which is why this policy is filed under the "bugs" theme with medium severity (peep "POLICY THEMES" in Perl::Critic).

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🔥 Builtins

Perl builtin functions with a newline always execute and hand you back their return value instead of the quoted word. periodt.

my %h = (print          # bad, builtin print() executes
         => "abc");
# %h is key "1" value "abc"

the builtin gets called with no arguments, and yeah that might throw a warning from some of them, but others like print will just quietly run like it owns the place 🙈

dashed builtin names such as -print are also function calls, just with a negate operator riding along 💅

my %h = (-print       # bad, print() call and negate
         => "123");
# h is key "-1" value "123"

for the purposes of this policy, the builtins are is_perl_builtin() from Perl::Critic::Utils. it's possible that's more builtins than the particular Perl you're actually running, but guarding against all of them will help you out if you ever go to a newer Perl in the future. future-proofing, we love to see it 👑

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🦋 Non-Builtins

in Perl 5.6 and earlier, all words foo execute as a function call when there's a newline before the fat comma.

sub foo {
  return 123
}
my %h = (foo
         => "def");
# in Perl 5.6 and earlier %h is key "123" value "def"

under use strict, an error gets thrown if no such function exists, the usual way. a word builtin is a function call if it exists (with a warning about being interpreted that way), or a bareword if it doesn't.

this policy prohibits all words with a newline before the fat comma when you're targeting Perl 5.6 or earlier. that means either an explicit use 5.006 or smaller, or no such minimum use at all. iykyk 💀

one subtle way an executing word with a newline before the fat comma can go undetected (still in 5.6 and earlier) is an accidental redefinition of a constant, and she's sneaky:

use constant FOO => "blah";
use constant FOO
  => "some value";
# makes a constant subr called blah (in Perl 5.6)

constant.pm might reject some return values from FOO(), like a number, but a string such as "blah" here quietly expands and creates a constant blah(). not me losing my mind over a silently-created sub 😭

the difference between Perl 5.6 and later Perl is that in 5.6 the parser only looked as far as a newline for a possible quoting => fat comma. in Perl 5.8 and later, for non-builtins, the lookahead keeps going beyond any newlines and comments. for Perl builtins the behaviour is the same across all versions — the lookahead stops at the newline. ok that's the lore, bestie, we know it now 🌈

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✨ Avoiding Problems ✨

putting the fat comma on the same line as the word ensures it quotes in all cases. simple as that 🎀

my %h = (-print =>    # ok, fat comma on same line quotes
         "123");

if for layout purposes you genuinely want a newline, the suggestion is to give a string or maybe a parenthesized expression, because that doesn't rely on the => fat comma doing the quoting. a fat comma can still emphasize a key/value pair, she still serves 💖

my %h = ('print'      # ok, string
         =>
         123);

alternately, if a function call is really what's intended (builtin or otherwise), then parens can be used in the normal way to make sure it's a call — as per perltrap, the rule being "if it looks like a function, it is a function" 👑

my %h = (foo()        # ok, function call
         =>
         123);

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🙈 Disabling

as always, if you don't care about any of this, you can disable "ProhibitFatCommaNewline" from your .perlcriticrc in the usual way (see "CONFIGURATION" in Perl::Critic):

[-CodeLayout::ProhibitFatCommaNewline]

slay, do what you want 💅

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🌟 SEE ALSO 🌟

• Perl::Critic::Pulp
• Perl::Critic
• perlop

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🏠 HOME PAGE 🏠

<http://user42.tuxfamily.org/perl-critic-pulp/index.html>

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📜 COPYRIGHT 📜

Copyright 2011, 2013, 2014, 2015, 2016, 2017, 2019, 2021 Kevin Ryde

Perl-Critic-Pulp is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

Perl-Critic-Pulp is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Perl-Critic-Pulp. If not, see <http://www.gnu.org/licenses/>.

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and that's the whole thing, bestie 🫶 this was perl v5.40.1, dated 2025-10-21, served to you with love from Perl::...Newline(3pm). go keep your fat commas cozy and stay iconic ✨💜