---
name: "Perl::Critic::Policy::InputOutput::ProhibitExplicitStdin"
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::ProhibitExplicitStdin"
---

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

Use "\<\>" or "\<ARGV\>" or a prompting module instead of "\<STDIN\>".

## NAME

Perl::Critic::Policy::InputOutput::ProhibitExplicitStdin - Use "\<\>" or "\<ARGV\>" or a prompting module instead of "\<STDIN\>".

## AFFILIATION

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

## DESCRIPTION

Perl has a useful magic filehandle called `*ARGV` that checks the command line and if there are any arguments, opens and reads those as files.  If there are no arguments, `*ARGV` behaves like `*STDIN` instead.  This behavior is almost always what you want if you want to create a program that reads from `"STDIN"`.  This is often written in one of the following two equivalent forms:

```
  while (<ARGV>) {
    # ... do something with each input line ...
  }
  # or, equivalently:
  while (<>) {
    # ... do something with each input line ...
  }
```

If you want to prompt for user input, try special purpose modules like IO::Prompt.

## 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 misses important cases like

```
  my $content = join '', <STDIN>;
```

because it interprets that line as the nonsensical statement:

```
  my $content = join '', < STDIN >;
```

When that PPI bug is fixed, this policy should start catching those violations automatically.

## CREDITS

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

## AUTHOR

Chris Dolan \<cdolan@cpan.org\>

## COPYRIGHT

Copyright (c) 2007-2023 Chris Dolan

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