When using boost::program_options, how does one set the name of the argument?

Question

When using boost::program_options, how do I set the name of an argument for boost::program_options::value<>()?

#include 

        

Answer 1

One can replace arg with something different via the global variable boost::program_options::arg:

boost::program_options::arg = "NUM";

But as that is a global variable, it doesn't help much to fix the problem when multiple option might require different arguments.