Thanks choroba, I didn't know about those Role::Tiny methods.

I am not sure about whether I prefer them to eval "with '$module'; 1;", though.

I had to load Role::Tiny explicitly not importing anything, since its before(), after(), around() and with() methods clash with Moo's :

Subroutine MyClass::before redefined at [...]/5.22.0/Role/Tiny.pm line
+ 58.
Subroutine MyClass::after redefined at [...]/5.22.0/Role/Tiny.pm line 
+58.
Subroutine MyClass::around redefined at [...]/5.22.0/Role/Tiny.pm line
+ 58.
Subroutine MyClass::with redefined at [...]/5.22.0/Role/Tiny.pm line 6
+7.
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And even when I do that I can't use apply_roles_to_object() inside sub BUILD, because the parent's methods haven't been loaded and thus the child's will be.

package MyClass::Child;

use Moo::Role;

sub foo { die 'horribly'; }
sub bar { return 'bar'; }

1;
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package MyClass;

use Moo;
use Role::Tiny();

sub BUILD {
    my $self = shift;

    Role::Tiny->apply_roles_to_object( $self, 'MyClass::Child' );

    return $self;
};

sub foo { return 'foo'; }

1;
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$ perl -MMyClass -E '$o = MyClass->new; say $o->foo, $o->bar;'
horribly at MyClass/Child.pm line 5.
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So the only way I could make it work as part of the Moo constructor was with apply_roles_to_package() :

package MyClass;

use Moo;
use Role::Tiny();

sub BUILD {
    my $self = shift;

    Role::Tiny->apply_roles_to_package( __PACKAGE__, 'MyClass::Child' 
+);

    return $self;
};

sub foo { return 'foo'; }

1;
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$ perl -MMyClass -E '$o = MyClass->new; say $o->foo, $o->bar;'
foobar
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Thanks again for the pointer.

Moo::Role is based on Role::Tiny. It means you can use

'Moo::Role'->apply_roles_to_package(...);
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There's no need to use Role::Tiny from Moo.

($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,
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Hi choroba,

That doesn't work for me. I had tried that because I knew that Moo::Role is based on Role::Tiny, but got an error:

package MyClass;

use Moo;
#use Role::Tiny();

sub BUILD {
    my $self = shift;

#    Role::Tiny->apply_roles_to_package( __PACKAGE__, 'MyClass::Child'
+ );
    'Moo::Role'->apply_roles_to_package( __PACKAGE__, 'MyClass::Child'
+ );

    return $self;
};

sub foo { return 'foo'; }

1;
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Output:

Can't locate object method "apply_roles_to_package" via package "Moo::
+Role" at MyClass.pm line 10.
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The way forward always starts with a minimal test.

Thanks, guys. This bit me tonight and the answer was exactly what you suggested.