You will have to do some more reading of the DBI docs.

They say about selectall_arrayref:

This utility method combines "prepare", "execute" and "fetchall_arrayref" into a single call. It returns a reference to an array containing a reference to an array (...snip...) for each row of data fetched.

As your SQL never returns more than one row with one field, you are probably rather looking for selectrow_array:

This utility method combines "prepare", "execute" and "fetchrow_array" into a single call. If called in a list context, it returns the first row of data from the statement.

So you code becomes:

my ($Count_A_ANY) = $dbh_B->selectrow_array( ... your SQL here ... );
[download]

How you link the first part of your code to the second part is a profond mystery to me, so I abstain from commenting.