$ ./qr-utf8.pl
              Rate qr//i+m// qr//+m//i  qr//+m//
qr//i+m//  10881/s        --      -98%      -98%
qr//+m//i 505263/s     4543%        --       -7%
qr//+m//  540845/s     4870%        7%        --