By default, duplicate elements in a collection are collapsed, as in the UNION of a set, and (as with sets) their insertion order is not (necessarily) preserved.

Sometimes it is desired, or necessary to return ALL the elements of a collection, in the order in which they were added.

How can you do this in a structured expression?

Here is an example I worked recently. I created an Opaque Behavior to mask part of an IP address (expressed as a string). Given a collection of strings, it returns a collection of strings that have been modified to obscure part of the address. What will frequently happen is that several of the returned string elements will have the same string value. Upon return, the duplicate strings have been collapsed into a single element.

How do you keep the Structured Expression from treating the final return value as a union of elements?

Note: neither the "Unique" nor "Ordered" collection settings seems to help.