Depends on how you did define it. The execute commands need to be defined seperately
<execute name="poweroff" allowParams="true">/home/pi/test.sh</execute>
so here the command is
@execute play
and it will run /home/pi/test.sh
important is to use full path and again it is run as user repetierserver. Means that path must be readable for that user (so all user read/execute permission must be set).