Tie::RefHash comes with perl.

I don't think I'd use Memoize.

Untested:

use Tie::RefHash; 
{
    tie my %refhash, 'Tie::RefHash'; 
    sub canonicalize_array { 
        my $ref = shift; 
        return $ref if exists $refhash{$ref};
 
        # Otherwise canonicalize the array.

        $refhash{$ref}++;  
        $ref;
    } 
}
[download]

Edit: Added the obvious $refhash{$ref}++; line.

-sauoq
"My two cents aren't worth a dime.";