How to tell if SQL stored in a variable will return any rows

If I have a SQL script stored in a variable like this:

DECLARE @SQL VARCHAR(MAX) = 'SELECT * FROM Employees WHERE Age > 80'

How can I tell if @SQL would return any rows if I were to run it?

In effect this:

IF EXISTS(@SQL) print 'yes, there are rows' -- Dummy code -- does not work!

I would like to try this without having to run the script in @SQL, insert that into a table and them count the rows.