$ perl -Mwarnings -MData::Dumper -e '
> @old = ( "10.5 AA", "9 AC", "2 BB");  
> @new = do {no warnings q/numeric/; sort {$b <=> $a} @old}; 
> print Dumper \@new;'
$VAR1 = [
          '10.5 AA',
          '9 AC',
          '2 BB'
        ];
$