---
name: "Perl::Critic::Policy::InputOutput::ProhibitJoinedReadline"
section: "3pm"
platform: "linux"
package: "perl-perl-critic"
version: "1.156-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/Perl::Critic::Policy::InputOutput::ProhibitJoinedReadline"
---

# Perl::Critic::Policy::InputOutput::ProhibitJoinedReadline(3pm)

Use "local $/ = undef" or Path::Tiny instead of joined readline.

## NAME

Perl::Critic::Policy::InputOutput::ProhibitJoinedReadline - Use "local $/ = undef" or Path::Tiny instead of joined readline.

## AFFILIATION

This Policy is part of the core Perl::Critic distribution.

## DESCRIPTION

It's really easy to slurp a whole filehandle in at once with `"join` `q{}, <$fh"`\>, but that's inefficient -- Perl goes to the trouble of splitting the file into lines only to have that work thrown away.

To save performance, either slurp the filehandle without splitting like so:

```
  do { local $/ = undef; <$fh> }
```

or use Path::Tiny, which is even faster.

**Note** that if the `"ProhibitPunctuationVars"` policy is also in effect, it will complain about the use of `$/` in the line above.  In that case, write this instead:

```
  use English '-no_match_vars';
  do { local $INPUT_RECORD_SEPARATOR = undef; <$fh> };
```

## CONFIGURATION

This Policy is not configurable except for the standard options.

## CAVEATS

Due to a bug in the current version of PPI (v1.119\_03) and earlier, the readline operator is often misinterpreted as less-than and greater-than operators after a comma.  Therefore, this policy only works well on the empty filehandle, `"<>"`.  When PPI is fixed, this should just start working.

## CREDITS

Initial development of this policy was supported by a grant from the Perl Foundation.

## AUTHOR

Chris Dolan \<cdolan@cpan.org\>

## COPYRIGHT

Copyright (c) 2007-2021 Chris Dolan.  Many rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.  The full text of this license can be found in the LICENSE file included with this module