Moose::Util::TypeConstraintsのSYNOPSISより： use Moose::Util::TypeConstraints; type 'Num' => where { Scalar::Util::looks_like_number($_) }; subtype 'Natural' => as 'Int' => where { $_ > 0 }; subtype 'NaturalLessThanTen' => as 'Natural' => …