I agree that you're probably better off just getting your opts out of the hash, but to clear up your initial comment, I'm pretty sure the (official/newest) way to declare it would be...

our $opt_u;

This makes it global and is necessary since you want to be accessing the same variable that Getopt is using.

-Bird

Update: Just read the comment by dws below. I was thinking of Getopt::Std. I have no idea how GetOpt works.