if (!$Session->{'isAuthenticated'})
{
    $Response->write( 'session is authenticated' );
    my $server_name = $Request->ServerVariables("SERVER_NAME")->item();
    $Response->write( "server name is '$server_name'" );

# ... etc ...
}

##</code><code>##

my $server_name = 'www.example.com';
my ( $prefix, $domain )
    = ( $server_name =~ m{ \A (\w+) \. (\w+) \. com }xms );
print "prefix: '$prefix'\n";
print "domain: '$domain'\n";