I can see two/three use patters now

• your demo: ad hoc definition of small but related OOP classes in a horizontal way (contrary to "vertical" inheritance)
• keeping the class' namespace clean of imported subs (kind of namespace::clean but right from the beginning)

• on a method basis
• without need of explicit import

{
    package Subs::I::Want;
    
    sub Target::Class::method {
         my ($self) = shift;
         $self->method2();  
         sub_I_want()
    }
}

{
    package Other::Subs::I::Want;
    
    sub Target::Class::method2 {
         other_sub_I_want()
    }
}
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hence

• Target::Class->method() or ->method2() work
• Target::Class->sub_i_want() or ->other_sub_I_want() won't work