my %help_options = (
   "color!" => sub { $options{USE_COLOR_CMDLINE} = $_[1] },
   "conf=s" => sub { $options{CONF} = $_[1] },
);
GetOptions( %help_options );

do  $options{CONF} if defined $options{CONF};

# Override it if specified on the command line.
$options{USE_COLOR} = $options{USE_COLOR_CMDLINE}
    if exists $options{USE_COLOR_CMDLINE};