An easy way? I don't know of one. But it should be possible.

What you'd have to do is save partial downloads, stare at the spec, and decide what the correct header is to send (you want a Range header, but you'll have to work out the parameters). Even then it will only work if the server supports range, which it might or might not. So test for that.

If you do this, then you'll be using the same technique that wget does. If you do this work, then it may be worthwhile to think hard about how to integrate the functionality either into LWP or WWW::Mechanize in some easy way. (Offhand I'd suggest having LWP have a get_with_retry which accepts parameters for its retry logic.)

Honestly I have to say that wget sounds like the solution that I'd be inclined to use.