Benchmarking a sort with array reference problem

[Edward Wijaya]

Hi,
I am trying to benchmark these two sorting algorithms.
However running the script below:
$ perl thiscode.pl
gives:
Can't use an undefined value as an ARRAY reference at radix.pl line 23.
However the code execute smoothly with the normal usage.
Only when I use 'cmpthese' the problem occur.
Any idea?
Thanks so much beforehand.
--
Edward WIJAYA
Singapore
__BEGIN__
#!/usr/bin/perl -w
use strict;
use Benchmark 'cmpthese';
my @array = qw(flow loop pool Wolf root sort tour);
#The script runs ok if I remove this 'cmpthese' snippet
cmpthese (-5, {rad   => "radix_sort([EMAIL PROTECTED])",
               nsort => "basic_sort([EMAIL PROTECTED])"
              }
         );
my @thear = basic_sort([EMAIL PROTECTED]);
print "@thear\n";
sub basic_sort {
 my $array = shift;
 my @ar2;
   @ar2 = sort @{$array};  #This is line 23, but seems that this is not  
the problem
  return @ar2;
}

sub radix_sort {
    my $array = shift;
    my $from = $array;
    my $to;
    # All lengths expected equal.
    for ( my $i = length ($array->[ 0 ]) - 1; $i >= 0; $i-- ) {
        # A new sorting bin.
        $to = [ ];
        foreach my $card ( @$from ) {
            # Stability is essential, so we use push().
            push @{ $to->[ ord( substr $card, $i ) ] }, $card;
        }
        # Concatenate the bins.
        $from = [ map { @{ $_ || [ ] } } @$to ];
    }
    # Now copy the elements back into the original array.
    @$array = @$from;
}


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