Plack::...re::Lint(3)

💖 Plack::Middleware::Lint — bestie edition 💖

okay so this is Plack::...re::Lint(3), from the User Contributed Perl Documentation girlies, and it's literally about catching your PSGI vibes before they go feral. let's get into it ✨

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✨ NAME ✨

Plack::Middleware::Lint — validate request and response 🎀

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🌸 SYNOPSIS 🌸

use Plack::Middleware::Lint;

my $app = sub { ... }; # your app or middleware
$app = Plack::Middleware::Lint->wrap($app);

# Or from plackup
plackup -e 'enable "Lint"' myapp.psgi

like, that's it. that's the whole vibe check ✨

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🦋 DESCRIPTION 🦋

so Plack::Middleware::Lint is a middleware component whose whole job is validating request and response environment formats. she's the friend who checks your outfit before you leave the house but for PSGI 💅

if you're out here building a new framework adapter or a new PSGI web server that implements the PSGI interface — bestie, you are strongly suggested to use this middleware. like, not optional energy. use it. fr fr.

and the best part?? this middleware is enabled by default when you run plackup or other launcher tools with the default environment value of development. she's already in the group chat whether you invited her or not 👑

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😭 DEBUGGING 😭

okay so here's the thing. because of how this middleware works, debugging Lint errors can be genuinely not easy when you hit one — unless you're out here writing a PSGI web server or a framework. no cap.

for example, when you're an application developer (aka a user of some framework) and you see errors like:

Body should be an array ref or filehandle at lib/Plack/Middleware/Lint.pm line XXXX

...there's literally no clue about which line of your application produces that error. it's giving mystery. it's giving ✨chaos✨. it's giving why.

we're aware of the issue, and there's a plan to spit out more helpful errors to diagnose the issue. but until then, currently there are some workarounds to make this easier 🫶

for now, the easiest one would be to enable Plack::Middleware::REPL outside of the Lint middleware, like:

plackup -e 'enable "REPL"; enable "Lint"' app.psgi

so that the Lint errors are caught by the REPL shell, where you can inspect all the variables in the response. she's holding your hand through it, iconic behavior 💜

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👑 AUTHOR 👑

• Tatsuhiko Miyagawa
• Tokuhiro Matsuno

the legends themselves 🌈

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🌟 SEE ALSO 🌟

• Plack

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and that's the whole page, bestie!! 💖

signing off with the receipts: this was perl v5.42.3, dated 2026-10-18, and yes the manual name is Plack::...re::Lint(3) — go validate those requests and responses, you absolute main character 🎀✨🦋💅