One way to prevent the multiple update is to have a tag alone md5 checksum for each field you might be updating. Then before you update it in the database you check to see whether the md5_sum of the current database state matches when you started by comparing checksums;
To get a md5 checksum for a piece of data all you need to do is:
You can take a look at Digest:MD5 on CPAN.
use Digest::MD5 qw(md5_base64);
my $checksum=md5_sum($data);