Perl marks an extreme of all the languages covered in this book. While some languages started with a clear set of powerful ideas (Lisp, C) or were designed carefully during years of research (ML, Haskell), Perl looks like a collection of solutions for a large number of small concrete problems. Perl's main characteristic is the context sensitivity which is related to Perl's use of funny symbols and which is always good for surprises. In this sense, it also marks the opposite of a pure functional language where everything has a well defined meaning independent of the context. Perl applications often are extremely stable software: Once you have created a large Perl application, it will be hard to find somebody willing to change it (including yourself).