I'd never used it before, but it looks like you need to access a value like this:

print $args->c, "\n";
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Tip #4 from the Basic debugging checklist: Data::Dumper

use Data::Dumper;
$Data::Dumper::Sortkeys=1;
print Dumper($args);

# outputs...

$VAR1 = bless( {
                 '-values' => {
                                'c' => '10',
                                'current_command' => undef,
                                'f' => 0,
                                'help' => 0,
                                'no_f' => 1,
                                'no_help' => 1
                              }
               }, 'Getopt::ArgParse::Namespace' );
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Note: your code does not compile.