when you move the file, doesn't that delete it?

from the File::Copy docs

    *   The "move" function also takes two parameters: the current nam
+e and
        the intended name of the file to be moved. If the destination
        already exists and is a directory, and the source is not a
        directory, then the source file will be renamed into the direc
+tory
        specified by the destination.

        If possible, move() will simply rename the file. Otherwise, it
        copies the file to the new location and deletes the original. 
+If an
        error occurs during this copy-and-delete process, you may be l
+eft
        with a (possibly partial) copy of the file under the destinati
+on
        name.

        You may use the "mv" alias for this function in the same way t
+hat
        you may use the "cp" alias for "copy".
[download]

of course unlink is failing!