Usually you do this type of thing because you want to replace the values, which I'd do like:

s{(<[^>]+>)|%([^%]+)%}{
    $1 || $replace{$2} // "%$2%"
}ge;
[download]

To just fetch the names, I'd do:

my @matches = grep defined, $data =~ m{<[^>]+>|%([^%]+)%}g
[download]

Avoiding complex constructs that are so easy to get wrong.