Perl code to detect googlebot from CGI

This routine detects Googlebot under a CGI environment. It also tests the remote address to make sure that the remote user really is from Google.

# In a CGI environment, this returns 1 if the remote user is
# googlebot, and undefined otherwise.

sub detect_googlebot
{
    my $user_agent = $ENV{HTTP_USER_AGENT};
    if ($user_agent =~ /googlebot/i) {
        my $remote_addr = $ENV{REMOTE_ADDR};
        if ($remote_addr =~ /^66\.249\./ ||
            $remote_addr =~ /^72\.14\./ ||
            $remote_addr =~ /^74\.125\./ ||
            $remote_addr =~ /^209\.85\./
# Use the following line to debug this.
#           || $remote_addr =~ /^192\.168\./
        ) {
            return 1;
        }
    }
    return;
}

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