sub usage
{
    my $err = shift and select STDERR;
    print "usage: ...\n";
    exit $err;
    } # usage

use Getopt::Long qw(:config bundling nopermute);
my $fldname;
my $dirname = "/tmp";
my $inline  = 0;
# etc ...
GetOptions (
   "h|help|?"    => sub { usage (0) },
   "v|verbose:1" => \$verbose,
   "f=s"         => \$fldname,
   "i"           => \$inline,
   "1=s"         => sub { read_structure_type ($_[1]) },
   ) or usage (1);