my @data;
while($sth->fetch) {
    push @data, {
        PK      => $_->[0],
        Name    => $_->[1],
        Memo    => $_->[2],
        Digest  => &digest($_->[2])
    };
}

# some time later...

foreach(@data) {
    print "PK:\t", $_->{PK}, "\t";
    print "Name:\t", $_->{Name}, "\t";
    print "Digest:\t", $_->{Digest}, "\n";
}