How to set variable in inline script (javascript)



I am trying to set variable in inline script but getting error. I have also tried execution.setVariable without task in front but that also threw same error. Is there anyway to do it in inline script. I have been looking for inline script documentation with examples but no luck. This seems to be very basic question.

Error: Cannot instantiate process definition test:22:9e5e7907-bfb4-11e8-acd3-0242ac170003: Unable to evaluate script while executing activity ‘Task_0bf014h’ in the process definition with id ‘test:22:9e5e7907-bfb4-11e8-acd3-0242ac170003’:ReferenceError: “task” is not defined in at line number 1


I had a typo in execution, so script works without task. Just :execution.setVariable(‘group’, ‘foo123’); is enough.