I can't think of a better discussion of typing issues than Dominus' Strong Typing and Perl talk. He knows a lot more about programming design than I do. In the talk, he argues that static typing (at least in C) is pretty much a failure. A very interesting alternative he brings up is a type-inferencing language like ML (or its variants). ML is a cool language if you have the chance to learn it, and I can attest to the fact that type inferencing really does help to avoid bugs.

In some senses, Perl really is strongly typed... at least in terms of scalars vs compound types. I seem to remember someone's sig around here that has a quote about Perl being strongly typed but not having many types. The best example of this is that a hash or array value must always be a scalar. Of course, Perl gives us references and does things like listification, so we hardly notice the distinction after a while.

In the end, I think it's really the polymorphism of the various scalar types (and not the lack of types) that lets us do all the things we love in Perl.