"...it repeats the data in database..."

Does that mean the same data is written twice or more to your database?

If so, i guess a bit :-( Can't you remember the mtime of dhcpd.leases and write the data only to your DB if dhcpd.leases was updated?

But this might get a little bit more complicated:

"...Every time a lease is acquired, renewed or released, its new value is recorded at the end of the lease file. So if more than one declaration appears for a given lease, the last one in the file is the current one..."

And:

"...In order to prevent the lease database from growing without bound, the file is rewritten from time to time. First, a temporary lease database is created and all known leases are dumped to it. Then, the old lease database is renamed /var/lib/dhcpd/dhcpd.leases~. Finally, the newly written lease database is moved into place..."

See also dhcpd.leases.

Update: Net::ISC::DHCPd::Leases might be interesting. I didn't use it but perhaps it's worth to take a look at.

Regards, Karl