in reply to use of DBI perl function fetchall_arrayref

Take a look at the perlref tutorial. Specifically Use Rule 1 applies directly to your question "how to access them"
Whatever you want to do with a reference, Use Rule 1 tells you how to do it. You just write the Perl code that you would have written for doing the same thing to a regular array or hash, and then replace the array or hash name with {$reference} .

In Section Seekers of Perl Wisdom