sub HashMPEG {
  # assign parameters useful names
  # $hArtist is a hash reference
  my ($f, $hArtist) = @_;

  #... extract data from MPEG file

  # -> operator is used when working with hash references rather
  # than hashes
  $hArtist->{_Get_Artist($m)}{_Get_Album{$m}}{_Get_Title{$m}}=\%TagInfo;

  # no need to return anything. artist is in hash reference
  # and caller has access to hash reference
}