How about:

Personally, though, I'd go for putting all your arguments in a hash, with a reference to the opt_arg value, the variable you want the final result in, and the default value, and use a for loop to rip through them setting them all. Perhaps include a type (numeric, string, flag) and do a little type checking. For instance, if someone passed '123' to the $opt_tcp value, it prolly ain't gonna work...

--Chris