You could use ARIN.net and then parse the results:

#!/the/world/is/my/Perl -w
use strict;
use LWP;
my $theIP = '206.170.14.76' #could easily be passed as a postarg or en
+vironment var
my $ua = new LWP::UserAgent;
my $req = new HTTP::Request 'POST', 'http://www.arin.net/cgi-bin/whois
+.pl';
$req->content_type('application/x-www-form-urlencoded');
$req->content('queryinput=', $theIP);

my $response = $ua->request($req);
&parse_resp($response);

sub parse_resp {
.....  # [HTML::Parser]
}
[download]