use strict;
use Net::DNS::Nslookup;

# ... do whatever you do open FH and load MYDB
#  (I'll fake it for now...)

my %MYDB = ( 'WWW.PERLMONKS.ORG' => 'TPF' );

while (<DATA>) {
    s/\s+$//;
    my @hostpair = split ' ';
    my $HOST = uc( $hostpair[0] );
    my $nslookup = Net::DNS::Nslookup->get_ips( $hostpair[0] );

    for my $addr ( split( /\n/, $nslookup )) {
        my ( $name, $ip ) = split( /,/, $addr );
        my $OWNER = ( exists( $MYDB{$HOST} )) ? $MYDB{$HOST} : "OTHER";
        print "$hostpair[0]\t$ip\t$OWNER\n";
    }
}

__DATA__
www.perlmonks.org
google.com