in reply to Fixing mp3 tags for Android 2.0

Some comments on your code...
  1. # We parse the command line to pick a directory, # this is easier my $start_dir = ".";

    How is that easier then my $start_dir = shift; ???

  2. Since $id3v1 and $id3v2 are both going to be objects, the distinction between undef and 0 isn't really relevant, so you should be able to simplify about 20 lines of initialization with something like...
    $id3v1 = $mp3->{ID3v1} || $mp3->new_tag("ID3v1"); $id3v2 = $mp3->{ID3v2} || $mp3->new_tag("ID3v2");
  3. Assigning default values like this...
    $artist = "Artist of $file_name";
    ...seems like the worst possible behavior you could have as a fallback. If instead you leave the fields blank, you can at least easily identify them later and you leave it up to the application to decide what to do about it (ie: display some string like "Unknown Artist", or prompty you, or try to fetch the metadata from an external music identification site).
  4. File::Find is your friend. It's been a core module for a while now, so you don't even need to worry about installing it.