Thanks. And from your comment ( http://arclanguage.com/item?id=4432 ) on the 8 Queens thread, the Ruby snippet in the OP above could be implemented as:
That said catch-throw is in ArcN, although they do have different intended usages. breakable: is supposed to be used as a modifier for existing control structures, while (catch ...) is supposed to be a control structure in its own right.