For example I put Carp::confess statements in some of my modules to catch internal errors. When my module works fine, there is simply no way to trigger them. They are dead code.

Still they are very useful, because when I change something and break the module, I get much better error messages than without those statements.

One could try to trigger thee cases by monkey-patching the module to misbehave, but I think that's a rather foolish idea.