You could use exec instead of system. If your system call is followed by exit the most "visible" change is that the END blocks won't be executed. It also means that you won't have a stack of calling scripts through which you'll have to go back at the end of the execution. An update will actually mean that your script is replaced by another instance, not that it waits for it to return.

You could also reload your script partially, ie keep the main package still, and reload modules while running with Module::Reload::Selective. I've never used it though, so I can't tell you much about it.

Is there a best way of having a script check to see if a new version of itself exists and updating it while running?

Yes, update a module :)

use App::Fantastic;
App::Fantastics->version_check_if_enabled;
App::Fantastics->run;
[download]

Is there a better way? Are there any pitfalls I might encounter?

:) Other than its annoying to be prompted for updates when you're trying to do stuff, offline?

I imagine there could be a race condition, or dns hijacking if you're not https-ing or something else :)

Evidently you can't switch while it's executed, but if you have the possibility to safely freeze, you could eval the code into an alternate namespace, and call the "main routine" there. (don't forget to empty the module before populating it)

You would flip-flop from Module_a to Module_b for each release.

Frozen data should be put into Module_Data.

Like this you wouldn't need to stop and start a process.

HTH!