cmpthese -1, { 
    A => q[ my @a = reduce{ $a += $b } 1 .. 1e4 ], 
    B => q[ my @a = reduce{ $a + $b  } 1 .. 1e4 ], 
};;
   Rate    B    A
B 315/s   -- -21%
A 399/s  27%   --

cmpthese -1, { 
    A => q[ my @a = reduce{ $a *= $b } 1 .. 1e5 ], 
    B => q[ my @a = reduce{ $a * $b  } 1 .. 1e5 ], 
};;
    Rate    B    A
B 13.3/s   -- -11%
A 15.1/s  13%   --