this isn’t just an academic curiosity. flip the alternation order to (ab|a)+ and suddenly PCRE matches the entire string! the | operator in backtracking engines is ordered - it’s not union, it’s “try left first”. the order of branches changes the result, which means | is not commutative. a|b and b|a can give different matches.
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On Feb. 10, the FBI released images and video taken from the Nest camera of a masked, armed individual on the property at the time of the disappearance. This individual was seen attempting to tamper with the camera by tapping it and eventually covering the lens with foliage. Despite these attempts at concealment, Google, which owns Nest, was able to successfully recover the footage from the device’s back-end systems.