Scalar::Readonly(3pm)

✨ Scalar::Readonly ✨

okay so bestie, this is a whole manual page for Scalar::Readonly, aka the little Perl module that does exactly one thing and does it slayfully: it hands you functions for controlling whether any scalar variable is read-only. that's it. that's the whole name. 💅

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🎀 SYNOPSIS 🎀

like, here's the vibe in code form:

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$]";

see that #ERROR!? yeah. no cap. she said no to that assignment. 👑

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💖 DESCRIPTION 💖

this module is simple. like, deliberately simple. it can make scalars read-only, which is genuinely useful if you've got config variables you want to protect from your own future self at 3am. 🫶

and here's the unhinged part: this module can also be used to subvert Perl's many read-only variables to potential evil trickery. yes, really. it said that. iconic behavior honestly. 😭

🌸 readonly

this function takes a scalar variable and tells you whether it is read-only.

• returns 0 if the scalar isn't read-only 👎
• returns a positive number if it is ✅

🌸 readonly_on

makes the passed scalar variable read-only. and if you then try to modify a read-only scalar, your code will die with this exact error message:

Modification of a read-only value attempted at

periodt. your program is done. it said what it said. 💀

🌸 readonly_off

makes the passed scalar variable read-write. 💫

bestie listen — you can even do this to read-only special variables, but you almost certainly don't want to do that. like, almost certainly. i'm just the messenger. 🙈

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🦋 EXPORT 🦋

• ':all' => readonly, readonly_on, readonly_off

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🌈 SEE ALSO 🌈

• Scalar::Util
• Attribute::Constant
• Const::Fast

go read those too, they're the friend group. 💜

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👑 AUTHOR 👑

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

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💌 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.

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and that's the whole page, babe 🎀 this was perl v5.42.3, dated 2026-08-19, and it's the Scalar::Readonly(3pm) manual — go make some scalars immutable and stay hydrated 💖✨