Term "Stream" usually used if variable is used as a stream,
    which means that output which is usually goes to 
    result text is redirected to a variable.
    In this case, we say that "stream" is open.

Output to result text is suppressed if even one stream is open.

To open stream x, the following action can be issued:

  .+x

A few streams can be open concurrently. For example:

  .+y  .+stream2 ...

To stop redirecting output data to a stream x, action 

  .-x 

can be issued.

To stop redirecting to all streams, action 

  .- 

can be issued.

To open stream "x" with initial x value x="",
action .*x can be used instead of .+x