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Scalar::Readonly(3pm) User Contributed Perl Documentation Scalar::Readonly(3pm)

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.

2024-10-15 perl v5.40.0