Right -- just make sure you include some appropriate message with the "die" call, because that is what $@ will be set to; e.g.:

eval { uploader( $dir, $name ) };
print "There was a problem uploading your file: $@" if ( $@ );

sub uploader {
    my ($upload_dir, $filename) = @_;
    ...
    open UPLOADFILE, ">$upload_dir/$filename"
        or die "Open for output failed on $upload_dir/$filename: $!";
    ...
    print UPLOADFILE ... or die "Output failed on $upload_dir/$filenam
+e: $!";
    ...
    close UPLOADFILE or die "Unable to close $upload_dir/$filename: $!
+";
    ...
}
[download]

If none of the die statements is invoked, $@ will come back undef and everything is fine; otherwise, $@ will be set to whichever message was passed to the die call, the thing uploader() was trying to do will have failed in some way, and the caller will keep running.