getopt ('switches'[, \%opts])switches is a string of the command-line options
that take arguments. For each option, getopt sets $opt_x
(where x is the switch) to the value entered as an argument.
If \%opts is specified, it is a reference to a
hash in which getopt sets the key to the name of the switch
and the value
to the argument (and the $opt_ variables are not set).