The method involves passing editor input to the external program, wherein {HEAD ~ the external program} evaluates {TAIL ~ the input}, produces either lines of output or zero lines of output, and transmits the output back to the editor 
evaluates
The method involves passing editor input to the external program , wherein { HEAD ~ the external program } evaluates { TAIL ~ the input } , produces either lines of output or zero lines of output , and transmits the output back to the editor
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH