I agree absolutely that there are often times when you need to check to see if something is defined in Perl. I was questioning the use of the test in a context where it looks like the variable should have been validated long ago - a rather bold interpretation of the example code I agree.

The important point here is to distinguish between cases where it is expected that a variable may be undefined as a result of previous processing (defined should be used to test that), and where a variable is undefined because of a flaw in previous processing - in which case use warnings catches the problem as early as possible and is extremly useful.

That's the point of my example; the fact that it throws a warning (or two)

In that case your example is gratuitiously idiosyncratic. The language provides a clean way of testing for a defined value. Why bend over backwards to avoid using defined?

While Its seldom a 'flaw in the code' if you need to check whether something has been defined, it is almost always a flaw in the code if use warnings generates an undefined used type warning. Comparing with undef is flawed, if only because you lose the virtue of turning on warnings.