That won't work for www.some.domain.com. Use a loop.

my $QNAME= "www.google.com"; 
 
my $QNAME_packed = '';
for my $part ( split( /\./, $QNAME ) ) {
   $QNAME_packed .= pack( 'C', length($part) ) . $part;
}
$QNAME_packed .= pack('C', 0)
[download]

Or

my $QNAME= "www.google.com"; 
 
my $QNAME_packed = '';
for my $part ( split( /\./, $QNAME ) ) {
   $QNAME_packed .= pack( 'C/a*', $part );
}
$QNAME_packed .= pack('C', 0)
[download]

Or

my $QNAME= "www.google.com"; 
 
my $QNAME_packed = '';
for my $part ( split( /\./, $QNAME ), '' ) {
   $QNAME_packed .= pack( 'C/a*', $part );
}
[download]

Or if requiring Perl 5.8 is acceptable

my $QNAME= "www.google.com"; 
 
my $QNAME_packed = pack( '(C/a*)*', split( /\./, $QNAME ), '' ) );
[download]