cmpthese -1,{
    a => q[ my $s='x'x11000; my@bits= unpack'(A6A5)*',$s;   ],
    b => q[ my $s='x'x11000; my@bits= $s=~m[(.{6})(.{5})]g; ],
};;
   Rate    b    a
b 427/s   -- -10%
a 471/s  11%   --