The symbol STOP is used to control whether the Pipeline actions run unattended, or
require a user input. In Widget mode, symbol STOP is defined by default as being
command PAUSE, requiring user input to continue. In pure pipeline mode
(PIPELINE * command), symbol STOP is defined as CONTINUE, so that action proceed
without any user intervention.
The user may override these default behviours by defining STOP either as
SYMBOL STOP CONTINUE
or
SYMBOL STOP PAUSE
before pipeline actions.
