Solutionunvalidated
then the variable should be copied (removing &). Tension: `msg.append(" World")` seems to modify `msg`. Outcome: the lambda must be mutable.
fe1a41af-959e-4ef3-bab1-219fb4f49808
then the variable should be copied (removing &). Tension: msg.append(" World") seems to modify msg. Outcome: the lambda must be mutable.