use strict;
use warnings;

use Getopt::Long qw( :config posix_default bundling no_ignore_case );

GetOptions('verbose|v' => \my $opt_verbose)
    or die("usage\n");

print( $opt_verbose || 0, "\n");

##</code><code>##

>perl 806754.pl -v
1

>perl 806754.pl --verbose
1

##</code><code>##

>perl 806754.pl -verbose
Unknown option: e
Unknown option: r
Unknown option: b
Unknown option: o
Unknown option: s
Unknown option: e
usage

>perl 806754.pl --verb
Unknown option: verb
usage

>perl 806754.pl -V
Unknown option: V
usage

>perl 806754.pl --Verbose
Unknown option: Verbose
usage