code: function zoneParser (span) {
    if (whitespace.test (span[0])) { return ["", span]; }
    var tokens = [];
    var sep = [];     // Separation indices.
    var section = toplevel (span);   // textual zones.
    while (section.zone !== null) {
      var zone = section.zone;
      // Add tokens before the zone.
      tokens = tokens.concat (span.slice (0, zone.from)
                                  .split (whitespace)
                                  .filter (nonEmpty));
      // Add the zone.
      tokens.push (span.slice (zone.from + 2, zone.to - 2));
      // Prepare for next iteration.
      span = span.slice (zone.to);
      section = toplevel (span);
    }
    tokens = tokens.concat (span.slice (0)
                                .split (whitespace)
                                .filter (nonEmpty));
    return tokens;
  }
docs: Cuts a control zone into an Array of Strings. We have three components: space-separated identifiers and text.