code: function append(source) {
              if (s === '') return;
              var index = 0,
                  expr = /\n/g,
                  s,
                  match;
              while (match = expr.exec(source)) {
                  s = source.substring(index, match.index+1);
                  if (s !== '') out.push('  write(\''+escapestr(s)+'\');\n');
                  index = match.index+1;
              }
              s = source.substring(index, source.length);
              if (s !== '') out.push('  write(\''+escapestr(s)+'\');\n');
          }
docs: Appends additional content to the program, if not empty