anything.
We could have left out the C<isa> option, but in this case, we are
-including ir for the benefit of other programmers, not the computer.
+including it for the benefit of other programmers, not the computer.
Next, let's move on to the C<parent> attribute:
In our case, we're making a new C<BinaryTree> object in our default,
with the current tree as the parent.
-Normally, when an object is instantiated, any defaults are evaluted
+Normally, when an object is instantiated, any defaults are evaluated
immediately. With our C<BinaryTree> class, this would be a big
problem! We'd create the first object, which would immediately try to
populate its C<left> and C<right> attributes, which would create a new