code: public static Tuple<Decl.Variable> determineModifiedVariables(Stmt.Block block) {
  		HashSet<Decl.Variable> modified = new HashSet<>();
  		determineModifiedVariables(block, modified);
  		return new Tuple<>(modified);
  	}
docs: Determine the set of modifier variables for a given statement block. A
  modified variable is one which is assigned.
  
  @param block
  @param scope
  @param modified