package Newton;
# methods and class attributes supported by all Newtons
...
sub be_famous {
}

package Issac;
# inherit things Newtons can do
@ISA qw(Newton);
# methods and class attributes supported by Newton::Issac instances
...
sub progress_physics {
}

package John;
@ISA qw(Newton);
# no methods/attributes, by themselves Newton::John's can just be famous (inherited from Newton)

package Olivia;
@ISA qw(John);
# methods and class attributes supported by Newton::John::Olivia instances
...
sub sing_like_a_bird {
}