The current file handle that <> is using is stored in ARGV, but my testing shows that perl has alrady closed ARGV when the while (<>) {...} loop terminates.

You might try checking $! to see if that gets set when the NFS server stops serving the file:

while (<>) {
  ...
}
# check $! which is probably from the last close
[download]

Update: ikegami pointed out that testing $! (as in if ($!) ... doesn't make sense here.

One issue is that $! is only set when there is an error. One way around this is to force a known error at the end of the loop so that you can tell if readline generated an error.

Update 2: One can assign to $!, so this should be able to detect if readline failed:

while (<>) {
  ...
  $! = undef;
}
if (defined($!)) {
  # $! contains error from last <c>close
[download]

} </c>