#!/usr/bin/perl --
use Data::Dump;
@num = @freq = 0..9;
dd\@freq,\@num;
{
    my @oldnum=@num;
    @num = sort { $freq[$b]<=> $freq[$a] } @num; 
    @freq[@oldnum] = @freq[@num];
    dd\@freq,\@num;
}
__END__
([0 .. 9], [0 .. 9])
(
  [9, 8, 7, 6, 5, 4, 3, 2, 1, 0],
  [9, 8, 7, 6, 5, 4, 3, 2, 1, 0],
)