On the other hand, if you're using Mo*, there might be cleaner ways how to achieve the same, e.g. applying roles to an instance at runtime:

'Moo::Role'->apply_roles_to_object($self, $read_only_class);
[download]

It reblesses the object behind the scenes, anyway. To disable the writers, you probably need to around them.

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]

If you apply a role,doesnt that comes as an addition to the object's properties/methods ? Or do you mean that the role has properties with the same name as in the class so they overwrite them ?

Changing the properties of the attributes works in the role:

#!/usr/bin/perl
use warnings;
use strict;

{   package MyRole;
    use Moo::Role;
    has +x => (is => 'ro');
}

{   package MyObj;
    use Moo;
    has x => (is => 'rw');

    sub finalize {
        'Moo::Role'->apply_roles_to_object($_[0], 'MyRole');
    }
}

my $o = 'MyObj'->new;
$o->x(12);

$o->finalize;
$o->x(13);  # x is a read-only accessor
[download]

Another way is to wrap the accessor:

{   package MyRole;
    use Moo::Role;
    requires 'x';
    before x => sub { die "x is read only" if @_ > 1 };
}
[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]

In most cases, yes. But, as a module user, I'd prefer it dying on erroneous operation rather than "asking politely".