MuS made a good catch by adding \s to capture multiple words in the pattern, including "BLD". I meant to do that originally, but I was only looking at two full events when I created the regex.
Addressing the problems question, in general, regex works best by matching patterns from left to right. Look-aheads, etc. are not that efficient and they require the pattern to exist or to not exist (less flexibility). Since this is Splunk, I assumed large datasets, and even small datasets can become large over time. Also, it is best to match as generally as possible in case the logs deviate from your test data.
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