our @a = @b = @c = @d = '00001' .. '10000';;

cmpthese -1,{
    a => q[ $_ += 0 for @a;], 
    b => q[ my @new; push @new, $_ + 0 while defined( $_ = shift @b ) ], 
    c => q[ $c[ $_ ] += 0 for 0 .. $#c; ], 
    d => q[ my @new = map $_ += 0, @d ] 
};;
       Rate        d        c        a        b
d     258/s       --     -58%     -72%    -100%
c     615/s     138%       --     -34%    -100%
a     932/s     261%      52%       --    -100%
b 4651085/s 1800042%  756579%  499189%       --