$object_instance -> set_state ( "here is a new state" );
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is translated by perl (because it knows it's a 'MyObject' because of that 'bless') into:

MyObject::set_state ( $object_instance, "here is a new state" );
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This is actually not quite true. "set_state" could be implemented in a base-class and in the general case that base-class might not be known at compile-time, so Perl cannot do any "translations" but actually has to perform a search for the proper method in the parent-class hierarchie at run-time.

At least that is my understanding...