Or you could be lazy and let Find::File do all the recursion and hard work.

use strict;
use File::Find;

#path can be relative to script dir or absolute path
my $MP3ROOT = 'my_music';
#my $MP3ROOT = 'C:\\My Documents\\My Music';

#regex is case insensitive
my $MP3SUFFIX = '.mp3';

my $PREFIX = 'http://www.homepage.org/';
#my $PREFIX = 'C:\\My Documents\\';

@ARGV = @ARGV || ( $MP3ROOT );

find( sub {
    if ( ( $File::Find::name =~ /$MP3SUFFIX$/i )
       and ( $File::Find::dir !~ /^\./ ) ) # discard .hidden dirs
    {
        print "<a href=\"$PREFIX$File::Find::name\">$_</a>\n";
    }
} , @ARGV );
[download]

Someone correct me if I'm wrong but this eliminates the need to keep track of operating system dependent file delims, too, doesn't it?