replacing the current value in the virtual type with {HEAD ~ the new value} identified in the instruction string using a process embodied in {TAIL ~ the computer program} 
replacing the current value in the virtual type with { HEAD ~ the new value } identified in the instruction string using a process embodied in { TAIL ~ the computer program }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL