open (EINLESEN, "<kjx2312.ght"); 
$passwort = <EINLESEN>; 

open (EINLESEN, "<kjx2312.ght"); 

open (EINLESEN, "<kjx2312.ght") or die $!; 

open (EINLESEN, "<kjx3212.ght");
$passwort = <EINLESEN>;
chomp ($passwort);
close (EINLESEN);
$z = 1;
while ($z<=3)
{
  print "\n";
  print "Bitte Kennwort (Versuch nr.: $z):";
  $eingabe = <>;
  chomp ($eingabe);
  if ($eingabe ne $passwort)
 {
   print "Leider falsch!!\n";
 }
 else
 {
   die "ok,Zutritt erteilt!\n";
 }
 $z++
}

#! /pfad/zu/perl.exe

use strict;
use warnings;

open (EINLESEN, "<kjx3212.ght") or die $!;
my $passwort = <EINLESEN>;
chomp ($passwort);
close (EINLESEN);

my $z = 1;
while ($z<=3){
   print "\n";
   print "Bitte Kennwort (Versuch nr.: $z):";
   my $eingabe = <STDIN>;
   chomp ($eingabe);
   if ($eingabe ne $passwort){
     print "Leider falsch!!\n";
   }
   else{
     die "ok,Zutritt erteilt!\n";
   }
   $z++
}

open (EINLESEN, "<kjx2312.ght") or die $1;

open (EINLESEN, "<kjx2312.ght") or die $!;

open (EINLESEN, "<kjx2312.ght") or die $1;

open (EINLESEN, "<kjx2312.ght") or die $!;

       $OS_ERROR
       $ERRNO
       $!      If used numerically, yields the current value of
               the C "errno" variable, or in other words, if a
               system or library call fails, it sets this vari-
               able.  This means that the value of $! is meaning-
               ful only immediately after a failure:

                   if (open(FH, $filename)) {
                       # Here $! is meaningless.
                       ...
                   } else {
                       # ONLY here is $! meaningful.
                       ...
                       # Already here $! might be meaningless.
                   }
                   # Since here we might have either success or failure,
                   # here $! is meaningless.

               In the above meaningless stands for anything:
               zero, non-zero, "undef".  A successful system or
               library call does not set the variable to zero.

               If used as a string, yields the corresponding sys-
               tem error string.  You can assign a number to $!
               to set errno if, for instance, you want "$!" to
               return the string for error n, or you want to set
               the exit value for the die() operator.  (Mnemonic:
               What just went bang?)

               Also see "Error Indicators".