As much as I love Perl and tend to use it for just about everything, making graphical desktop applications is not widely regarded as one of its strengths and I do not believe that Learning Perl goes into GUI programming at all. I do have a separate book (also from O'Reilly), Learning Perl/Tk on that topic, but, while I have read the book, I have not done enough with Tk programming to have any real sense of how good the book's information may be.

If, however, you're interested in making web-based applications, Perl is an excellent choice. The last chapter of Learning Perl covers CGI programming, which is the fundamental method of creating web-based applications in Perl, and there are many other books (as well as tutorials here on perlmonks) covering CGI for once you're comfortable with the basics of the language.