sub walk {
     my ( $ref ) = @_;
     return "$ref" if blessed $ref;
     given ( ref $ref ) {
          when ( '' ) { return $ref; }
          when ( 'ARRAY' ) { return map { walk($_) } @$ref; }
          when ( 'HASH' ) { return map { $_ => walk($ref->{$_}) } keys %$ref; }
          default { carp "I'm confused by $ref" }
     }
}