Переименование файлов для удаления последовательностей в скобках

echo "Type one of the following words:"
echo "even, odd, zero, negative"
while :; do
  read varword
  varword="${varword,,}" #downcase it
  case "$varword" in
    even|odd|zero|negative)
      echo "The approved word you have selected is $varword, great work! "; break;;
    *)
      echo "The unapproved word you have selected is $varword, Please try again.";;
  esac
done