The bgp-peer entry is an array of hashes. You can access them in a similar way that you access a hash of hashes (which you seem to have got the hang of):

• hash of hash - $xml->{'bgp-information'}->{'bgp-peer'}
• hash of arrays - $xml->{'bgp-information'}->{'bgp-peer'}->[0]

Have you read the Perl data structures cookbook? And have a look at Data::Dumper. It's invaluable when dealing with deeply nested structures.