Another system allows {HEAD ~ an operator} to vary {TAIL ~ the width} of a mark from an initial dimension 
to vary
Another system allows { HEAD ~ an operator } to vary { TAIL ~ the width } of a mark from an initial dimension
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH