other example for debug_on() method

[borisdaeppen]

this also works

$plugin->debug_on(  sub {
                        my ($package, $filename, $line) = caller;
                        print "$package\t$_[0]\n";
                    }   
                 );  

and is more elegant. Can be shown in the examples!

[borisdaeppen]

done. will be available soon with version 0.5