You could try using an alarm (untested code) 
$SIG{ALRM} = sub { die "Seems hung"; };
# 30 seconds
alarm(30);
if (open(TESTFILE, $testfile)) {
  alarm(0); # disable alarm
}

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Edit: Make sure to listen to Fletches advice below as well.

In reply to Re: How to monitor an NFS mount with perl by cowboy
in thread How to monitor an NFS mount with perl by w3ntp

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