my $opt = 'ah1:2:3:f:l:L:i:d:';
my ($isascii, $fmtfile, $fldname, $length, $location, $infile, $dirname);
getopts ("$opt", \%opt);

switch ($_) {
        case {$opt{1}} { read_structure_type1($opt{1}); next; }
        case {$opt{2}} { read_structure_type2($opt{2}); next; }
        case {$opt{3}} { read_structure_type3($opt{3}); next; }
        case {$opt{f}} { $fldname = $opt{f}; next; }
        case {$opt{l}} { $length  = $opt{l}; next; }
        case {$opt{L}} { $location = $opt{L}; next; }
        case {$opt{i}} { $infile  = $opt{i}; next; }
        case {$opt{d}} { $dirname = $opt{d}; next; }
        case {$opt{h}} { usage(); exit;            }
}