If the files are missing ID3 tags, then there is really no way to get that data from the files themselves. If all the files use a common naming convention, you might be able to parse Artist & Track name from the file name and save that into the ID3 tag -- I assume that's what you're trying to do.
my ($Artist, $Track) = $Filename =~ /(.*) +- +(.*)\.mp3/i;