pod2usage(-verbose => 1) && exit if defined $opt_help;

##</code><code>##

pod2usage(-verbose => 1) if defined $opt_help;

##</code><code>##

    print "$0: input_file required\n";
    pod2usage(-verbose => 0) && exit

##</code><code>##

    pod2usage(-verbose => 0, -message => "$0: input_file required\n")