sub scanDir {

    print "scandir() aufgerufen! \n";
    
    # open current directory

    local *CURDIR;
    opendir(CURDIR, ".") or die "could not open directory $! \n";
    
    # iterate over directory entries
    
    while(my $dirEntry = <CURDIR>) {

        # skip "." and ".."
    
        if($dirEntry eq "." || $dirEntry eq "..") {
            print "skipping . and ..! \n";
            next;
        }

        # if we encounter a audio-file
    
        if(-f $dirEntry && $dirEntry =~ m/(.*mp3$)|(.*ogg$)/) {
            print "renaming file! \n";
            renFile($dirEntry);
        }
    
        # if we encounter a directory, descend into it and start recursion    
    
        elsif(-d $dirEntry) {
            chdir($dirEntry) or die "could not open directory $dirEntry! \n";
            print "descend into next directory! \n";
            scanDir();
        }
    
    }

    close(CURDIR);    

    return 0;
}