There's some rationale here[0]. Basically they'd need to use a parser that on ambiguities would have to go down all possible routes concurrently until all but o

There's some rationale here[0]. Basically they'd need to use a parser that on ambiguities would have to go down all possible routes concurrently until all but one fail, which can lead to performance costs. Using a prefix keeps things simple. [0] https://wiki.php.net/rfc/arrow_functions_v2#x_x_y1 https://wiki.php.net/rfc/arrow_functions_v2#x_x_y1