Interestingly that only two lines differ in execution times. What is common in these two lines and what differs from other lines? I see the only difference that both slowered 'if's ('if' and 'elsif') proceed to non-empty expressions.
swl guessed (Re^2: regex gotcha moving from 5.8.8 to 5.30.0?) that performance could be influenced by '^' (and its interplay with '\s*'). I see that 3rd and 4th regexes also have '^', but they do not influence speed of execution(!?). My guess is if '\s* ^ \s*' is somehow cached after executing 2nd regex and then 3rd and 4th regexes use the result of 2nd's(?). And very strange that 1st regex executes slowly. Can it be because of '\Z' being a kind of a relative to '^'...

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