In general, it's a Good Idea to "capture the capture variables" immediately after a match in order to avoid these kinds of strange problems:

if ($string =~ m{ (foo|bar) (\d+) (w[ia]g) }xms) {
    my ($one, $two, $three) = ($1, $2, $3);
    do_something_with($one);
    ...
    }
[download]

if (my ($one, $two, $three) = $string =~ m{ (foo|bar) (\d+) (w[ia]g) }
+xms) {
    do_something_with($one);
    ...
    }
[download]