controlTraceTo :: History -> History -> Either String [Expression]
controlTraceTo start end =
    impureCmd (\worker -> controlTraceToWorker worker start end) start
controlTraceTo :: History -> History -> Either String [Expression]
controlTraceTo start end =
    impureCmd (\worker -> controlTraceToWorker worker start end) start
controlTraceTo start end =
    impureCmd (\worker -> controlTraceToWorker worker start end) start