package Servant::PartlyJustDelegating;

has callback_proxy => (
    is => 'ro', isa => 'CodeRef', required => 1,
);

BEGIN {
    for (qw( invent_example fail_admittedly )) {
        no strict 'refs';
        my $callback = $_;
        *$callback = sub {
            goto &{ shift->callback_proxy->($callback) };
        };
    }
}

package Omnipotential::Entity;

has servants => (
    is => 'ro',
    isa => 'ArrayRef[Servant::PartlyJustDelegating]',
);

has _servant_interface_proxy => (
    is => 'ro',
    isa => 'CodeRef',
    lazy => 1,
    builder => '__build_servant_interface_proxy',
    init_arg => undef,
);

sub __build_servant_interface_proxy {
    my ($self) = @_;
    weaken($self); 
    my %callback_for = (

        invent_example => sub {
            my $part = shift;
            ...
        },

        fail_admittedly => sub {
            my ($part, $arg) = @_;
            ...
        },

    );

    return sub {
        my $name = shift;
        return $callback_for{ $name } //
            croak "callback not found: $name";
    };

}

sub _build_servant {
    my ($self, $row) = @_;
    ...
    return Servant::PartlyJustDelegating->new(
        @arguments,
        callback_proxy => $self->_servant_interface_proxy,
    );
}