code: function sequence ( parserSyntax ) {
  				var i, res,
  					originalPos = pos,
  					result = [];
  
  				for ( i = 0; i < parserSyntax.length; i++ ) {
  					res = parserSyntax[i]();
  
  					if ( res === null ) {
  						pos = originalPos;
  
  						return null;
  					}
  
  					result.push( res );
  				}
  
  				return result;
  			}
docs: Try several parserSyntax-es in a row. All must succeed; otherwise, return null. This is the only eager one.