On top of everything said by those more experienced monks above, you need to be careful when blessing an object that it actually matches one of your package names...

    bless($self, "Adult");

should be...

    bless($self, "Person::Adult");
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or even simple code that is not relying on your dynamic typing will fail:

my $a = Person::Adult->new(NAME => 'the hard way');
$a->sayHi();
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