use XML::Simple

suppose I have a .passwds.xml file like this:

<?xml version="1.0"?>
<users>
 <user>
  <uid>0</uid>
  <name>root</name>
  <passwd>123456</passwd>
  <identity>root</identity>
 </user>
 <user>
  <uid>1</uid>
  <name>test</name>
  <passwd>123456</passwd>
  <identity>root</identity>
 </user>
</users>

and I can use the following perl script to parse it and determin whether a user can login

#!/usr/bin/perl
use XML::Simple;

$passwds = ".passwds.xml";

my $xmlobj = new XML::Simple(KeyAttr=>[]);

my $data = $xmlobj->XMLin("$passwds");

my $loggedin = -1;

my $username = "test";

my $password = "123456";

foreach  (@{$data->{"user"}}){
 if (($_->{"name"} ne $username)){
  next;
 }
 $loggedin = 0;
 if ($_->{"passwd"} eq $password){
  $loggedin = 1;
 }
 last;
}
if ($loggedin == -1){
 print "username incorrect\n";
 die;
}
if ($loggedin == 0){
 print "password incorrect";
 die;
}
print "successfully login\n";

strlen&sizeof

strlen is a function calculating the length of a string,i.e.,'\0' excluded,
while sizeof is an operator calculating a variable's size when compiling,i.e.,if affect on a string,'\0' will be included.
just as is shown in this little programme:

#include <stdio.h>
#include <string.h>

#define s "hello"
int main ()
{

  printf ("strlen:%d\n",strlen (s));
  printf ("sizeof:%d\n",sizeof (s));
  return 0;/*thank u,anonymous,haha*/
}

after executed,it outputs:
strlen:5
sizeof:6