As far as I know it should be safe to seek() and tell() on the handle without any problems under normal conditions. *

It's possible that other modules (like source filters) may mess with this strategy, but using it in your own code should work.

* update: it's even possible to seek to the beginning of the file and read the source before the __DATA__ line, and as far as I know that's a documented feature (though there probably isn't really a *good* reason to use it).

update 2: for some more caveats see the beginning of the SelfLoader documentation.