perl -w -MData::Dumper -e '
@old = ( "10.5 AA", "9 AC", "2 BB");  
@new = sort {($b =~ /(\d+)/)[0] <=> ($a =~ /(\d+)/)[0]} @old; 
print Dumper \@new;

##</code><code>##

use Data::Dumper;
@old = ( "10.5 AA", "10.6 AA", "9 AC", "2 BB");  
@new = sort {($b =~ /(\d+)/)[0] <=> ($a =~ /(\d+)/)[0]} @old; 
print Dumper \@new;

##</code><code>##

$VAR1 = [
          '10.5 AA',
          '10.6 AA',
          '9 AC',
          '2 BB'
        ];

##</code><code>##

use Data::Dumper;

use strict;
use warnings;

my @old = ( "10.5 AA", "10.6 AA", "9 AC", "2 BB");  
my @new;
{
	no warnings;
	@new = sort {$b <=> $a} @old; 
}
"a" == "a"; #meaingless other than to demo the fact that the warnings is back on
print Dumper \@new;