I agree, except in your assertion that the hash brute-force method is best.

Performance wise the hash method will always take O(n) time, even if the first and second elements of the lists are different. An appriach like what I present below can bail-out if it finds a mismatch before examining the entire list. Therefore giving it a better average and best-case performance for lists that don't have homogeneous contents.

sub is_list_homegeneous{
  my @list=@_;
  my $val=shift @list;
  foreach(@list){
    return 0 if($_ ne $val)
  }
  return 1;
}
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This is not as short and cool, but does have better algorithmic performance. You could tweak-out the overhead I incurred by copying the list if you wanted the utmost in speed. My technique is probably slightly slower worse-case (a homogeneous list), because it does do slightly more work.