# rename files to 01.mp3, 02.mp3, etc.
my @mp3list = 
   process_files( { function => "mv", message => "renaming", extension => "\.mp3", list => @list } );
 
# call mpg123 to convert .mp3 to .wav
my @wavlist = 
   process_files( { function => "mpg123", param => "-qw", message => "converting", extension => "\.wav", list => @mp3list } );
 
# call sox to convert each .wav to .cdr
my @cdrlist = 
   process_files( { function => "sox", message => "converting", extension => "\.cdr", list => @wavlist } );