Not much. (: Urm, that is, I haven't previously thought much about the design of LWP. Since I've only used LWP a bit, I guess that is only a small indication of a reasonable design.

Looking over my experience with it I'd have to say that I don't recall any real problems and that the design seems quite good.

I guess my major worry about someone looking at LWP to learn OO in Perl would be that LWP is quite large, making analysis of its design more difficult.

I also worry that LWP's success with inheritance may encourage the use of inheritance which I find is best avoided for most problem domains, at least in Perl where the only supported inheritance is implementation inheritance which is the kind that I, and others, really have a problem with.