Thinking again of my suggestion, a dummy module is here not the way to go. The problem is that "use feature" usually introduces new syntax, and there's no way to make this working in older perls (other than using a source filter, shudder).

If somebody wants to use the new 5.10.0 and remain backwards-compatible, then probably it's best to have the code in two files and have a:

if ($] >= 5.010) {
    require "new_style.pm";
} else {
    require "old_style.pm";
}
[download]

Which means duplication of code. I think this is only useful if the new features have significant advantages like better performance.