Param Substitution in Stream Expressions?

[James Greene]

My application relies on local parameter substitution pretty heavily due to
escaping issues and being able to re-use clauses.

Is there any way to use param substitution in a /stream expression?

(This doesn't work):

POST /stream {
  'expr': 'search(collection1,q=$test,fl="doc_id",sort="doc_id
asc",qt="/export")',   'test': 'contains:blah'
}



Cheers,
JAG