The Specio distribution provides classes for representing type constraints and coercion, along with syntax sugar for declaring them. Note that this is not a proper type system for Perl. Nothing in this distribution will magically make the Perl interpreter start checking a value's type on assignment to a variable. In fact, there's no built-in way to apply a type to a variable at all. Instead, you can explicitly check a value against a type, and optionally coerce values to that type.