Variables can only be reset using the mapping functions ClearVariable, ClearVariables or ClearAllVariables(see below) , since a rule with an empty string is not executed!
ClearAllVariables (['ExlcudeVariablenName1, ExlcudeVariablenName2'])
Resets all variables:
ClearAllVariables()
Resets all variables except variables named HeaderGln and HeaderSupplier:
ClearAllVariables ('HeaderGln, HeaderSupplier')