class Cache::LRU {
    use Hash::Ordered;
    our      $num_caches = 0;                    # class data (unused in this example)
    my       $x          = Hash::Ordered->new;   # private instance data
    has UInt $max_size   = 20;                   # public instance data

    method set ( Str $key, $value ) {
        if ( $x->exists($key) ) {
            $x->delete($key);
        }
        elsif ( $x->keys > $max_size ) {
            $x->shift;
        }
        $x->set( $key, $value );
    }

    method get ( Str $key) {
        return unless $x->exists($key);
        return $x->set( $key, $x->delete($key) );
    }
}