package JustTesting;

use strict;
use warnings;

use Moose;
use MooseX::Types::Moose -all;

has 'data' => (
    is      => 'ro',
    isa     => CodeRef,
);

##</code><code>##

Attribute (data) does not pass the type constraint because: Validation failed for 'ArrayRef|RegexpRef|Str|HashRef' with value CODE(0x25d85c0) ...