fcn makeList(separator){
  counter:=Ref(1);  // a container holding a one. A reference.
  // 'wrap is partial application, in this case binding counter and separator
  makeItem:='wrap(item){ c:=counter.inc(); String(c,separator,item,"\n") };
  makeItem("first") + makeItem("second") + makeItem("third")
}

print(makeList(". "));