Well, I poked around a bit more, and it turns out that when the error handler is called with the statement handle, that latter is pretty much already destroyed. So much so that "Type" (which should be 'st' for that kind of handle, according to the DBI documentation) isn't defined. And I guess that serves as a de facto version of the check I was asking about. If I just return without doing anything in that case, I still get the doubled error message, but the exception throws just fine from the other call. I guess that's what I'll go with for now.