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   hkey => sub{
        my @range = (keys %{+{map {($_ => 1)}0 .. $N-1}})[0 .. $K-1];
   }

perl randomshuffle.pl 10 5
          Rate  samp  hkey  shuf   mpu
...
shuf  934174/s  762%  652%    --  -27%
mpu  1275273/s 1077%  927%   37%    --

 
perl randomshuffle.pl 100 5
          Rate  hkey  samp  shuf   mpu
...
shuf  212991/s 1244%  621%    --  -86%
mpu  1519656/s 9491% 5043%  613%    --