This module uses Data::Flow interface, thus one uses it in
the following fashion:

     $c = new C::Scan(attr1 => $value1, attr2 => $value2);
     $c->set( attr3 => $value3 );

     $value4 = $c->get('attr4');

Attributes are depending on some other attributes. The
only required attribute, i.e., the attribute which should
be set, is filename, which denotes which file to parse.
