Updating a XML Column

DECLARE @newValue varchar(50)
SELECT @newValue = 'NewValueXX'
UPDATE [temp1]
SET request_data.modify('replace value of (/request_data/segment/text())[1] with sql:variable("@newValue")')
Where request_data.value(' (/request_data/segment)[1]', 'varchar(50)' ) like 'ta%'