extract a hostname from a fqdn

[iang]

I have to extract a hostname from a fqdn, however it is possible that the fqdn is simply a hostname. so for host.foo.bar.com, I want to split (host,domain). and for host , I want to split, but domain should be null. I realize that I can do this with split, but I wanted to try a regex. My code is like this:

if($file =~ m/hd_defect-(.*?)\.(.*)$/) {
   $host = $1;
   $dom = $2;
}

this does not work for a simple host, so I added a modifier:

if($file =~ m/hd_defect-(.*?)\.?(.*)$/) {
   $host = $1;
   $dom = $2;
}

But that does not work either. Any pointers would be appreciated. Thanks