Why doesn't this work?
Read up on the return value of s/// in scalar context.
That doesn't apply. both m// and s/// return values that can be interpreted by a while() construct to evaluate to a boolean. The point isn't what the s/// expression returns, it's whether matching (then substitution) ia done "progressively" as the documentation says it would for m// in the context of a while() loop. The fact that the documentation doesn't say anything about s/// (at least, not in the ORA perl book) leads me to consider it to be either an oversight in implementation, or an outright bug. :-/
calls to other functions have to be made
What do you think sprintf is? The body of the loop is the replace expression. Put the die in there.
No, that would be involved and overly obfuscated. Granted, it
can be done, and there's no question that perl is robust enough that you could implement any solution using its existing implementation. but just because there's "another way to do it" is not a good reason to always defend an aspect to the current design that may be potentially... well, "undefined".
I'm not trying to be argumentative; I'm only trying to focus on this one aspect of s/// and how "progressive matching" has been defined/implemented. I appreciate the explanations for how ELSE to accomplish the task, but that's not what I'm hoping to discuss.