cmpthese -1,{
    a => q[ my $s='x'x1100; my@bits= unpack'(A6A5)*',$s;   ],
    b => q[ my $s='x'x1100; my@bits= $s=~m[(.{6})(.{5})]g; ],
};;
    Rate   b   a
b 4516/s  -- -6%
a 4780/s  6%  --