I don't think you can ever learn
Perl, but you can get more proficient the more you do. That said, the reason I did suggest the 21 day book is I know a couple of people it did well for. Personally I learned via the camel, but it was the textbook for the class that I took.
And yes there are a bunch of lousy Perl books out there, the Dummies Guide being one of the worst IMHO. However, I still think that for the person with little or no programming experience, O'Reilly tends to be a bit heavy.
Just my opinion.
There is no emoticon for what I'm feeling now.