docs: def p_block(p):
      """block : '{' commands '}' """
      # section 3.2: REQUIRE command must come before any other commands,
      # which means it can't be in the block of another command
      if any(command.RULE_IDENTIFIER == 'REQUIRE'
             for command in p[2].commands):
          print("REQUIRE command not allowed inside of a block (line %d)" %
              (p.lineno(2)))
          raise SyntaxError
      p[0] = p[2]