Rather than creating a comparison for each possible bad return code, we can simplify this:
```bash
BAD_RETURNS=( 0 253 254 255 )

for val in "${BAD_RETURNS[@]}"; do
  if [ $RETVAL -eq $val ]; then
    echo "Cannot retry.  Quitting."
    exit                                                                        
  fi  
done

echo "Retrying..."
sleep 2

let COUNTER=COUNTER+1
```

It does that same thing but avoids having to add more comparisons, in the future, if there are other return codes that should be a fail fast.