The first two lines simply produces a two-event sample.
Field emul is populated using numerals between 10000 and 20000. The first event will contain a string roughly 5,000x6 byte=30,000 byte long, whereas the second event contains a string roughly 10,000x6 byte=60,000 byte long.
The intent of the two cascaded rex commands is to utilize text behind double curly braces whenever possible.
Because the two events are structurally identical, I expect both to produce bar /stuff. Such is the case when the second mvrange() is up to mvrange(10000,19000), or ~9,000x6 byte=54,000 byte. Not much longer than that, output becomes
short bar /stuff
long foo}} bar /stuff
In other words, the second rex fails to take effect. (The last two commands simply shorten output and have no effect on whether the second rex fails or not.) I see no error in job inspector and such. In my real-world search, complicated subsequent commands, including rex, do not appear affected, even after the equivalent of "Begin:.+}} (?.+)" fails.
Is this a bug or is there some parameter I need to tweak? What is special about "Begin:.+}} (?.+)"?