my %actions = (
    '000005' => {
                    '1205' => [ 58, 62, ... ],
                    '1210' => [ 56, 60, ... ],
                    ...
                },
    '000015' => {
                    '1215' => [ 28, 30, ... ],
                    '1230' => [ 26, 28, ... ],
                    ...
                },

);

...

my $action = $actions[$field[11];
if ($action) {
    my $action2 = $action->{$timestamp};
    if ($action2) {
        my ($maxarray, $field_ix, $whatever_else) = @$action2;
        if ($arraysize > $maxarray and $field[$field_ix] eq '') {
            ....
        }
        else {
            ....
        }
    }
    else {
        ....
    }
}
else {
    ....
}