code: def p_let_arr_substr_in_args4(p):
      
      i = 2 if p[1].upper() == 'LET' else 1
  
      id_ = p[i]
      arg_list = p[i + 2]
      substr = (arg_list.children.pop().value, p[i + 4])
      expr_ = p[i + 7]
      p[0] = make_array_substr_assign(p.lineno(i), id_, arg_list, substr, expr_)
docs: statement : LET ARRAY_ID LP arguments TO expr RP EQ expr
                    | ARRAY_ID LP arguments TO expr RP EQ expr