Perl::Critic error "Readonly version 21 required"

[7stud]

First try with Perl::Critic. According to cpan here, the latest version of Readonly is 1.03. How do I get rid of the Readonly error along with the rest of them:

package CriticMy;

use strict;
use warnings;
use 5.010;

use criticism 'gentle';
use Readonly my $unprintable => 0x15;    #***LINE 8*****

our $VERSION = 1.00;

1;

--output:--
Use of uninitialized value $_ in pattern match (m//) at /Users/7stud/p
+erl5/perlbrew/perls/perl-5.16.0/lib/5.16.0/Exporter.pm line 57.
Use of uninitialized value $_ in exists at /Users/7stud/perl5/perlbrew
+/perls/perl-5.16.0/lib/5.16.0/Exporter.pm line 57.
Use of uninitialized value $_ in pattern match (m//) at CriticMy.pm li
+ne 8.
Use of uninitialized value $sym in hash element at CriticMy.pm line 8.
Use of uninitialized value $sym in pattern match (m//) at CriticMy.pm 
+line 8.
Use of uninitialized value $sym in substitution (s///) at CriticMy.pm 
+line 8.
Use of uninitialized value $sym in hash element at CriticMy.pm line 8.
Use of uninitialized value $sym in concatenation (.) or string at Crit
+icMy.pm line 8.
Readonly version 21 required--this is only version 1.03 at /Users/7stu
+d/perl5/perlbrew/perls/perl-5.16.0/lib/5.16.0/Exporter/Heavy.pm line 
+120.
BEGIN failed--compilation aborted at CriticMy.pm line 8.

[kcott]

G'day 7stud,

I think you're main problem there is syntax. Compare

$ perl -Mstrict -Mwarnings -e '
use Readonly my $unprintable => 0x15;
'
Readonly version 21 required--this is only version 1.03 at /Users/ken/
+perl5/perlbrew/perls/perl-5.14.2_WITH_THREADS/lib/5.14.2/Exporter/Hea
+vy.pm line 120.
BEGIN failed--compilation aborted at -e line 2.

with

$ perl -Mstrict -Mwarnings -e '
use Readonly;                        
Readonly my $unprintable => 0x15;
'

I don't have the criticism module installed; however, I don't think the problem is related to Perl::Critic. See how you go with the altered syntax.

[7stud]

Arghh! Thanks. After changing that, and then changing my constant to all upper case, I didn't get any errors. But when I use criticism 'brutal', I get:

Code is not tidy at CriticMy.pm line 1.

I think I should be able to sort that out.

[tobyink]

Note:

0x15 == 21

[tobyink]

It seems Exporter (which Readonly, and many, many, many, many other modules use internally) has a weird feature (in my opinion a misfeature) where it does its own module version number checking.

Normally when you write:

use Module 1.23;

... perl will catch the version number, and not treat it as an argument to Module->import, instead passing it to Module->VERSION to act as a version number check.

However, it seems Exporter makes an attempt to catch number-like arguments that perl has missed, and do its own version checking with them. Notice the difference between the following two examples; the first one where the version check is done by perl, and the second where it's done by Exporter.pm

$ perl -e'use Carp 100 ()'
Carp version 100 required--this is only version 1.26 at -e line 1.
BEGIN failed--compilation aborted at -e line 1.

$ perl -e'use Carp () => 100'
Carp version 100 required--this is only version 1.26 at /home/tai/perl
+5/perlbrew/perls/perl-5.16.2/lib/5.16.2/Exporter/Heavy.pm line 120.
BEGIN failed--compilation aborted at -e line 1.

In your original example, this line:

use Readonly my $unprintable => 0x15;

... is run as:

use Readonly undef => 0x15;

... because the variable is undefined. So Exporter's version number check kicks in, even though the 0x15 was clearly never intended as a module version number.

Yet another reason to avoid using Exporter and use something sane like Sub::Exporter.

[7stud]

Sheesh. I had no idea what your previous post meant. Thanks for the explanation.