---
name: "Scalar::Readonly"
section: "3pm"
platform: "linux"
package: "libscalar-readonly-perl"
version: "0.03-2+b2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Scalar::Readonly"
---

# Scalar::Readonly(3pm)

functions for controlling whether any scalar variable is read-only

## NAME

Scalar::Readonly - functions for controlling whether any scalar variable is read-only

## SYNOPSIS

```
  use Scalar::Readonly ':all';
  my $foo = "foo";
  readonly_on($foo);
  $foo = "bar";  #ERROR!

  if (readonly($foo)) {
    readonly_off($foo);
  }

  readonly_off($]);
  $] = "6.0";

  print "This is Perl v$]";
```

## DESCRIPTION

This simple module can make scalars read-only. Useful to protect configuration variables, for example.

This module can also be used to subvert Perl's many read-only variables to potential evil trickery.

### readonly

Ths function takes a scalar variable and tells you whether it is read-only. It returns 0 if the scalar isn't read-only, and a positive number if it is.

### readonly\_on

Makes the passed scalar variable read-only. If you try and modify a read-only scalar, your code will die with the following error message:

```
  Modification of a read-only value attempted at
```

### readonly\_off

Makes the passed scalar variable read-write. You can even do this to read-only special variables, though you almost certainly don't want to do that.

### EXPORT

':all' =\> readonly, readonly\_on, readonly\_off

## SEE ALSO

Scalar::Util, Attribute::Constant, Const::Fast.

## AUTHOR

Philippe M. Chiasson, \<gozer@cpan.org\>

## COPYRIGHT AND LICENSE

Copyright (C) 2004 by Philippe M. Chiasson

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.3 or, at your option, any later version of Perl 5 you may have available.