the ! syntax means a "mutually exclusive trigger". the trigger will hide all of the elements at the same level as the triggered item.
In this case it means "right arm", "right arm", "left arm", "left arm", "overall", "torso and shoes" and "pants" all get hidden when the trigger occurs. If you mean to just replace the two arms, put those two pieces of artwork into their own group.
You can read more about about key triggers on page 25 of the help document here
Thank You Very Much Daniel