my $timeout = time+$X;  # timeout if we don't see anything in $X seconds
my $ttl_bytes_rcvd=0;   # haven't received anything yet
while (time < $timeout) {
   ... read the data ...

   if ($bytes_read>0) {
      $timeout = time+$X; # Reset timeout if we actually saw some data
      $ttl_bytes_rcvd += $bytes_read;
   }

   # don't just hammer the CPU, give other processes a chance to do something,
   # as well as allowing a bit of time for more data to arrive
   sleep 0.5;
}
if ($ttl_bytes_rcvd) {
   # process successful response
   ...
}
else {
   die "Error!  No data received!\n";
}