Used hydrogen peroxide mouthwash a few times yesterday and today have extremely dry tongue, loss of taste and producing very little saliva. can the mouthwash cause permanent damage?

No, it should not. The mouthwash cannot damage the salivary glands. Your tongue and oral mucosa are too sensitive to the mouthwash you used, symptoms will resolve by time.

Reaction may be due to strength of solution. Stop using until you can discuss your issues with your Dentist. Any mouthwash is not a substitute for proper oral hygiene, both brushing and especially flossing. Your symptoms should resolve in time, but you must discuss this with hour Dentist.