$ 03_01_flag_bool --help
clap [..]
A simple to use, efficient, and full-featured Command Line Argument Parser
USAGE:
03_01_flag_bool[EXE] [OPTIONS]
OPTIONS:
-v, --verbose
-h, --help Print help information
-V, --version Print version information
$ 03_01_flag_bool
verbose: false
$ 03_01_flag_bool --verbose
verbose: true
$ 03_01_flag_bool --verbose --verbose
verbose: true