|%~ arm door hoon hoon .. hoon ==||Evaluate an arm in a door.|
|~(arm door hoon hoon .. hoon)|
%~ Evaluates an arm in a door.
A door is a sort of core which has one or more arms and takes a sample. (A gate is a trivial case of door, with only one arm, $.)
When %~ is used, which we'll often see as in its irregular form as ~(arm door hoon hoon ..), all of the hoon expressions will be taken as the sample for evaluation the specified arm.