I have weired problem when i ping a domain name which is hosted at the server. I get response

unknown host mydomain.com

Its weired because its the domain which is hosted at server.

So what is causing this and how to resolve it?

Though i ping to google.com or any other site returns with proper ip addresses.

What server? Your own website? What exactly are you trying to achieve? I think you need to describe what it is you want to do in more details. It is quite possible your domain name hasn't propagated yet, if it is a new purchase that is. Or possible routing issues.

I am talking about my dedicated server which is unmanaged from web hosting company. Yes i am talking about websites which are hosted on that server.

I can ping every site except those which are hosted at same server. It returns

ping: unknown host mydomain.com

I purchased that server about 6 days before and transferred sites from previous server so i think its enough for dns propgation.

Actual problem is that my perl script cannot access local file using LWP::Simple -> get function. I believe its because of above mentioned issue because ping returns unknown host instead of correctly retrieving ip address.

Your help and guidance is really appreciated.

Can you view the websites via your browser? Is everything else letting your host resolve to your dedicated server IP? Have you opened a shell local / on your dedi and typed the command:

host www.yourdomain.com

If it returns something like it did for my google query below, then you can rule out an issue with DNS propogation or configuration, as long as the IP shown is that of your server. If it doesn't, then you have an issue with your DNS configuration either local on the server or in the nameserver settings placed in the domain name registrar:

bash-3.1$ host www.google.com
www.google.com is an alias for www.l.google.com.
www.l.google.com has address 64.233.183.147
www.l.google.com has address 64.233.183.103
www.l.google.com has address 64.233.183.99
www.l.google.com has address 64.233.183.104

Sorry, I meant to add, this won't return anything if there is an issue with the hostname being resolved as it checks to see if what it is trying to connect to is a valid domain.