trace add variable ::errorInfo write traceScalar
   catch {set dne}
   lrange [set info] 0 2
} -cleanup {
   # always remove trace on errorInfo otherwise further tests will fail
   unset ::errorInfo
} -result {::errorInfo {} write}



# append no longer triggers read traces when fetching the old values of
# variables before doing the append operation. However, lappend _does_
# still trigger these read traces. Also lappend triggers only one write
# trace: after appending all arguments to the list.

test trace-3.1 {trace add variable read-modify-writes} {