|Contains external variables to be bound to a query
. Variable names and values are separated by equality signs, and multiple variables are delimited by commas. Variables may optionally be introduced with a leading dollar sign. Commas that occur in the value itself are encoded by duplication. If a variable uses a namespace different to the default namespace, it can be specified with the [http://www.jclark.com/xml/xmlns.htm Clark Notation] or [http://www.w3.org/TR/xquery-30/#id-basics Expanded QName Notation].