Are there any special considerations when mixing fn:put with transform expressions?

Example 1
---------

copy $dummy := <dummy />
modify fn:put(<new-document />, "output.xml")
return local:non-updating-query()

This stores an element in output.xml but also returns the result of executing a non-updating query.  

It seems a little unfortunate that this 'dummy' is required to mix fn:put with a non-updating query - although since this is essentially an expression with side effects, perhaps that's no bad thing.

Example 2
---------

let $original := doc('update.xml')
return
  copy $doc := $original
  modify (insert node <node /> into $doc/nodes, fn:put($doc, "update.xml"))
  return $original

This example reads and writes the same resource.  In XSLT, there is a specific (recoverable) error which mentions a similar situation with xsl:result-document.

[ERR XTRE1500] It is a recoverable dynamic error for a stylesheet to write to an external resource and read from the same resource during a single transformation, whether or not the same URI is used to access the resource in both cases. 

Example 3
---------

copy $doc := doc('update.xml')
modify (insert node <node /> into $doc/nodes, fn:put($doc, "update.xml"))
return (count($doc/nodes/node), count(doc('update.xml')/nodes/node))

Because 'doc' is stable the two calls to doc must return the same result, even though an update has occurred.

Example 4
---------

copy $doc := <a />
modify (fn:put($doc, "update.xml"))
return doc('update.xml')

Does doc('update.xml') see the newly created resource, or the original resource (if we assume one was available)?