You have to put them where you want them. In your example that would be

my @stuff;

sub wanted {
    push @stuff, $File::Find::name
        if -f && ! -d && m/\.mp3$/i;
}

find(\&wanted, $mp3_dir);
[download]

or better

my @stuff;

find(sub {
    push @stuff, $File::Find::name
        if -f && ! -d && m/\.mp3$/i;
}, $mp3_dir);
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Except it isn't better, since all you're doing is to process them one by one. So do it right in the callback function:

find(\&wanted, $mp3_dir);
                                                                      
+          
sub wanted {
    return unless -f && ! -d && m/\.mp3$/i;

    print "$File::Find::name\n"

    my $mp3 = MP3::Mplib->new($item);
    my $v1tag = $mp3->get_v1tag;
    my $v2tag = $mp3->get_v2tag;
                                                                      
+          
    while (my ($key, $val) = each %$v1tag) {
        print "$key\: $val\n";
    }
    while (my ($key, $val) = each %$v2tag) {
        print "$key\: $val\n";
    }
}
[download]

Update: That should be push @stuff, $File::Find::name, not push @stuff, $_, otherwise you loose the path.