Sounds like the real problem is not the upload, but trying to store upload. Why don't you just try to copy the file and let $! report the error for you? If $! is defined, then the copy did not work and will contain a (good enough) reason to report back to the user. For the most part, the upload either worked or it didn't so I don't feel the need to tell a user all the many reasons why it didn't work. 9 times out of 10 the upload didn't work due to permission problems (that's a bug) and the other 1 is hitting the max upload limit. Is it really your responsibility to keep them from uploading empty files? What if they really wanted to upload an empty file?

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)