use v6;

class animal {
 has $.legs;
 submethod new($l) {return self.bless(*, :$l)}
 submethod BUILD(:$l) {
  legify($l);
  multi legify(Int $l) {$!legs = $l}
  multi legify($l) {$!legs = $l.legs}
 }
}

class pet is animal {
 has $.name is rw;
 submethod new($x) {return self.bless(*)}
}

my $spider = animal.new(8);
say $spider.legs;
$spider = pet.new($spider);
say $spider.legs;