Command-line interface (CLI) applications often require both global and subcommand-specific flags to provide flexible user input and functionality. Using the Go standard library's `flag` and `FlagSet` types, developers can cleanly separate global flags, which apply to all subcommands (such as a `precision` flag for setting decimal output), from flags relevant only to particular commands (such as an `absolute` flag for the `subtract` subcommand, returning only positive results regardless of argument order). This structure allows for intuitive interfaces similar to popular tools like Git, where each subcommand can offer unique flag options. Implementation involves defining dedicated `FlagSet` instances for subcommands, providing granular argument parsing and targeted help messages without polluting the global flag space. Key takeaways include the importance of thoughtful flag scope, the limitations of flag parsing order with the standard library, and the advantages of frameworks like Cobra for building scalable, user-friendly CLI tools. Upcoming exercises extend these concepts by introducing mutually exclusive global flags for output formatting and a subcommand-specific flag for the division remainder, reinforcing best practices in CLI design.