querying TLD nameservers - limitations

[blrmaani]

I am developing a monitoring script for internal use and this requires extensive querying of TLD nameservers (a .. m).tld servers.

Questions:
1. Are there any rate limitations imposed by TLD servers i.e these servers allows only certain number of DNS queries per IP per second?

2. Are there other limitations I should be aware of while developing my script?

Any experience among this group members in developing these kind of scripts using Net::DNS::Resolver perl module?

Thanks!
Blr