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.
Implementers shouldn't need to jump through these hoops. When you find yourself needing to relax or bypass spec semantics just to achieve reasonable performance, that's a sign something is wrong with the spec itself. A well-designed streaming API should be efficient by default, not require each runtime to invent its own escape hatches.
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Россия нарастила до максимума вывоз одного лакомства«Ведомости»: Экспорт шоколада из России достиг почти млрд долларов в 2025 году
O’Leary argues this is a “horrific signal” in Gen Z hiring trends. He said it shows younger professionals can’t think or make decisions on their own.