That makes no sense. An empty list isn't false. Or true. It's not a scalar, so those concepts don't apply to it. You can't evaluate whether an empty list is true or false. You can only evaluate if a scalar is true or false.

As such, if you're trying to get a true or false value from those operators, you would be evaluating them in scalar context, and the following is what the listed operators actually return in scalar context:

• grep returns the count of matching elements.
• map returns the count of elements it would return.
• m// and s/// return success or not.