if (not -d $delTemp) {
  unlink $delTemp;
}
[download]

Unfortunately, this opens the door for race conditions (see https://en.wikipedia.org/wiki/Time_of_check_to_time_of_use). The documentation that you cited shows that it is save to use unlink even on directories. It will simply fail. You won't notice, though, because you don't check for errors here. (Just add or die "Can't unlink $delTemp: $!" after unlink $delTemp).

There is only one way to make unlink dangerous, and all of the following must happpen:

1. use an operating system that allows unlinking a directory
2. be root
3. start the script with perl -U script.pl or change the shebang line to include the -U flag

A quick search shows that Linux does not unlink directories, but returns EISDIR instead. FreeBSD behaves the same. OpenBSD seems to allow unlinking directories, depending on the filesystem, but only for root. NetBSD seems to behave like OpenBSD.

Alexander