Just an observation.
I tried a couple of different things using 2k with regards to this.

With opendir (DIR, "a:") || die "could not access floppy: $!"; It prompts me twice to insert a disk and then dies gracefully - I would assume on 9x or NT it would give the abort retry fail error 2 times.

With open (PIPE, "dir /od a: |") || die "Could not access floppy: $!"; It does not die, and gives me an error message after the script exits.

Useless info, as you already have an answer, but interesting. I'd be curious to see whether the opendir function behaves better for you.