sub set_normalized_designation {
    my $self = shift;
    my $designation = shift;

    $self->ensure_normalization($designation);
    $self->{normalized_designation} = shift;
}

sub ensure_normalization {
    my $self = shift;
    my $designation = shift;
    $designation =~ /.../ or
        die "$designation is not correctly normalized";
}

##</code><code>##

class Thing {
    my $.title is rw;
    my $.standard_directory is rw; # Where graphics etc are found
    my $.designation is rw;
    my Hash $.def;                 # Use another class?
    
    method normalized_designation { 
        my $normalized_des = $.designation;
        $normalized_des =~ s/.../.../;
        return $normalized_des;
    }
}