_BRUN is not a valid named constant

SetCommand() with _B or _BRUN can not be compiled.

I understand that script is somewhat strange place to call script control commands.
However, there is nothing wrong with, for example, script restarting itself if something goes terribly wrong.
And second, the documentation clearly indicates that it should be possible, because it has an example:

Syntax Scripting: setcommand(_R, nn)
setcommand(_BRUN, nn)