Make a copy of {expr}. For Numbers and Strings this isn't different from using {expr} directly. When {expr} is a |List| a shallow copy is created. This means that the original |List| can be changed without changing the copy, and vice versa. But the items are identical, thus changing an item changes the contents of both |Lists|. A |Dictionary| is copied in a similar way as a |List|. Also see |deepcopy()|. Can also be used as a |method|: mylist->copy()