use HTML::LinkExtor;
my @links = ();
my $html = join'',<DATA>; # much more elegant than => do { local $/; <DATA> };

sub extract_links {
    my ($tag,undef,$url) = @_;

    if($tag eq 'a') {
        push @links, $url->host;
    }
}

my $p = HTML::LinkExtor->new(\&extract_links,'http://foobar.com');
$p->parse($html);

print join "\n", @links;

__DATA__
<a href="http://www.foo.com">description</a>
<a href='http://www.foo.com'>image here</a>
<A href='http://foo-bar-publishers.co.uk'>image here</a>