That was it. I ran a sniffer trace and found that the request was sending in the header "IF-Modified-Since" which was causing google.com to send a reply with html code 304 (Not Modified). So I modified my last subroutine loop where I request the image url as follows -

my $img_url = $attr->{src};                             
my $remote_name =URI->new_abs($img_url,$parser->{base});
                                                        
my $local_name=$remote_name->host . $remote_name->path;
mkpath(dirname($local_name),0,0711);                   
                                                        
print "Getting imagefile: $img_url\n";                  
$request  = HTTP::Request->new(GET => $remote_name);    
my $response = $browser->request($request, $local_name);
                                                        
print STDERR "YYY-$local_name: ",$response->status_line,
[download]

It works now. Thanks to everyone for their input.