While mail at mbaierl dot com makes the point that this function isn't best for reporting the possible error condition of the most recently executed step, there are situations in which it is especially helpful to know the last error—regardless of when it occurred.
As an example, imagine if you had some code that captured the output from dynamic pages, and cached it for faster delivery to subsequent visitors. A final sanity check would be to see if an error has occurred anywhere during the execution of the script. If there has been an error, we probably don't want to cache that page.
