use strict;
use warnings;
use Data::Dumper;

my @test_data = (
    { a=>1, b=>2 },
    { ab => 12}
);


my %unique = map { my @k=sort(keys %$_); 
                   join("",@k, @$_{@k})
                    => $_ } 
                   @test_data;
print Dumper [values %unique];

##</code><code>##

$VAR1 = [
          {
            'ab' => 12
          }
        ];