sub parse_command_line {
    my ($opt_backlink,...,$opt_verbose);
 
    unshift @ARGV, split ' ', $Config{pod2html} if $Config{pod2html};
    my $result = GetOptions(
                       'backlink!'  => \$opt_backlink,
                       ...,
                       'verbose!'   => \$opt_verbose,
    );
    usage("-", "invalid parameters") if not $result;
    ...
}