I disagree. More specifically while I agree that encapsulation is possible without OO, I believe that most of the advantages that most programmers saw when they moved to OO was that they began to use more encapsulation because it became simpler to do so.

I also disagree that you can't do polymorphism without OO. There are plenty of ways to write code such that you'll get polymorphism. One obvious approach is to emulate how OO works by hand (this turns out to be fairly simple).

About multiple inheritance, it sounds to me like you think that MI is a great idea, but it just keeps on not coming up as a good solution for you. However I'm going to guess that if you ran across a problem today that looked like what you used it for 9 years ago, you'd probably find that there was a perfectly good single inheritance solution available that you now have the programming maturity to find.

Also note that I differentiate multiple inheritance from attempts to create mixins. For one thing mixins have the distinct advantage that you avoid the complications around how to decide which method to dispatch to when unrelated parents implement different versions. Since most of my complaints about MI have to do with exactly that problem, avoiding it does not seem to me to be a small change in semantics.

That said, I generally don't like mixins in Perl, though I do in Ruby. The difference, as I've said many times, is how many uses I can amortize the effort of learning the interface over.