I've only read the first few chapters but like it so far. I'm by no means an expert so I feel like your target audience. Generally speaking, the tone is good. I can wade right in with you.
A couple minor points that I will point out which may have been corrected already:
Chapt. 3: variables paragraph, last sentence, used the word "genericity". I suggest "genericness" instead.
Chapt. 3: variables, types and coercion section, it says "assigning to a variable". I assume that should read "assigning type to a variable"?
Chapt. 3. var, types and coercion section, your note "should I include a table of escapes here..?". Why not reference the table here if it is used elsewhere?
I look forward to getting through the rest of the book. Writing about perl 5.10.1 is a good idea, not only because I could benefit from it but it appears overlooked.