@for and @forall decorators

[eelstork]

Currently there isn't a decorator for applying an action to a list of target objects.
For example, if we had an IEnumerable list of waypoints, we may wish to visit all waypoints in turn; maybe something like:

@for(waypoints)?[ Reach ]  // Reach: Func<T, status>

@forall would do the same assuming parallelism.