Stream Variable ?
This wildcard is replaced with the value of a previously set, temporary variable. These temporary variables must be set within the stream and are only available while the stream is running.
Temporary variable exist only in the current, running stream.
Although it is possible to forward them to another stream via Job Create Job Action or Stream Execute Generic Stream Action. In case the following stream is setting a temporary variable with the same name, the previous one will be overwritten!
Use of the wildcard
The wildcard is used in the following ways:
Variable name: test1
Variable value: hello
{stream.variable.?}
For the following input (?) --> test1
{stream.variable.test1}
The output is going to be --> hello