I don't believe programs can handle as much randomness as you're suggesting... [...] The second pass to glue things together should change the result from a twitching mass of random code to something that at least runs to completion.
I personally believe that... whoa! what you describe is an entirely different game altogether: which is not to say it wouldn't be interesting or fun. But I explained the goals of the game as I see them in my reply to graff's comment, which expressed similar concerns as yours: to be fair I'm specifically interested and I think that people who would like to play an autenthically "Exquisite Corpse" version of the game should be specifically interested in the "twitching mass of random code" getting out of it! (Thank you for contributing this very illuminating expression!)
Since both you and graff, reasonably, point at subs, I recognize that as an alternative to the "last statement rule" a player may give a sub call of a sub he didn't include in his portion of the script, for the next one to write one. But I wonder if that couldn't be too restrictive of his freedom of could turn the game, if all players choose to handle "continuations" that way into a boring series of nested sub calls... Perhaps a restriction should be imposed to the effect that this kind of continuation can not be given for more than one turn. Thus a player writing the "requested" sub may or may not actually end it or leave it open, and write further code beyond it or not: scary! ;)