Return::Type allows you to specify a return type for your subs. Type constraints
from any Type::Tiny, MooseX::Types or MouseX::Types type library are supported.

The simple syntax for specifying a type constraint is shown in the "SYNOPSIS".
If the attribute is passed a single type constraint as shown, this will be
applied to the return value if called in scalar context, and to each item in the
returned list if called in list context. (If the sub is called in void context,
type constraints are simply ignored.)