But, naturally, I do not know the expected size of your 5000 clobs. If, for instance, 1 clob is maximally 64kB and 350MB of memory is acceptable for your Perl process, let you pull 5000 rows at once... When I implemented data replication between MySQL, Postgres and MSSQL servers, I have chosen 1000 maxrows.

I use the result mostly in this manner:

my $aref = $sth->fetchall_arrayref();
foreach (@$aref) {
    #now $_ is ref to an array holding one result row
    for (my $i = 0; $i < @$_; $i++) {
        print "$i: $_->[$i]\t";
    }
    print "\n";
}
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$$aref[0] or $aref->[0] is the first item of the "upper" array, i.e. reference to the array containing first data row,

$$aref[$rowindex][$colindex] or $aref->[$rowindex]->[$colindex] is the $colindex'th item of $rowindex'th data row.

Primarily, you should know if it sounds reasonably :>) It depends on many factors, typically, size of the data, network latency and bandwith and speed of the SQL query (i.e. query optimization, Oracle configuration, frequency of processors, amount of memory, ...) If it is 100MB of the data, 7 min could be O.K. in my opinion.

Note If you use fetchall_arrayref with maxrows or other method which does NOT pull all data at once, do not forget to pull all remaining data using, for instance, fetchall_arrayref repeatedly, or call $sth->finish(). I do not know Oracle internalities, but, it is very honest to say "Thank you, the server, I do not need remaining data."