my $gross = -s "datei.txt" or die $!; 
print "Größe ist $gross\n";

Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
  Platform:
    osname=MSWin32, osvers=5.00, archname=MSWin32-x86-multi-thread
    uname=''
    config_args='undef'
    hint=recommended, useposix=true, d_sigaction=undef
    usethreads=define use5005threads=undef useithreads=define usemultiplicity=define
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cl', ccflags ='-nologo -GF -W3 -MD -Zi -DNDEBUG -O1 -DWIN32 -D_CONSOLE -DNO_STRICT -DHAVE_DE
S_FCRYPT -DNO_HASH_SEED -DUSE_SITECUSTOMIZE -DPRIVLIB_LAST_IN_INC -DPERL_IMPLICIT_CONTEXT -DPERL_IMP
LICIT_SYS -DUSE_PERLIO -DPERL_MSVCRT_READFIX',
    optimize='-MD -Zi -DNDEBUG -O1',
    cppflags='-DWIN32'
    ccversion='12.00.8804', gccversion='', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=8
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='__int64', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='link', ldflags ='-nologo -nodefaultlib -debug -opt:ref,icf  -libpath:"C:\Setup\Perl\lib\CORE
"  -machine:x86'
    libpth=\lib
    libs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib  comdlg32.lib advapi32.lib sh
ell32.lib ole32.lib oleaut32.lib  netapi32.lib uuid.lib ws2_32.lib mpr.lib winmm.lib  version.lib od
bc32.lib odbccp32.lib msvcrt.lib
    perllibs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib  comdlg32.lib advapi32.li
b shell32.lib ole32.lib oleaut32.lib  netapi32.lib uuid.lib ws2_32.lib mpr.lib winmm.lib  version.li
b odbc32.lib odbccp32.lib msvcrt.lib
    libc=msvcrt.lib, so=dll, useshrplib=true, libperl=perl58.lib
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -debug -opt:ref,icf  -libpath:"C:\Setup\Pe
rl\lib\CORE"  -machine:x86'


Characteristics of this binary (from libperl):
  Compile-time options: MULTIPLICITY PERL_IMPLICIT_CONTEXT
                        PERL_IMPLICIT_SYS PERL_MALLOC_WRAP
                        PL_OP_SLAB_ALLOC USE_ITHREADS USE_LARGE_FILES
                        USE_PERLIO USE_SITECUSTOMIZE
  Locally applied patches:
        ActivePerl Build 822 [280952]
        Iin_load_module moved for compatibility with build 806
        PerlEx support in CGI::Carp
        Less verbose ExtUtils::Install and Pod::Find
        Patch for CAN-2005-0448 from Debian with modifications
        Rearrange @INC so that 'site' is searched before 'perl'
        Partly reverted 24733 to preserve binary compatibility
        MAINT31223 plus additional changes
        31490 Problem bootstraping Win32CORE
        31324 Fix DynaLoader::dl_findfile() to locate .so files again
        31214 Win32::GetLastError fails when first called
        31211 Restore Windows NT support
        31188 Problem killing a pseudo-forked child on Win32
        29732 ANSIfy the PATH environment variable on Windows
        27527,29868 win32_async_check() can loop indefinitely
        26970 Make Passive mode the default for Net::FTP
        26379 Fix alarm() for Windows 2003
        24699 ICMP_UNREACHABLE handling in Net::Ping
  Built under MSWin32
  Compiled at Jul 31 2007 19:34:48
  @INC:
    C:/Setup/Perl/site/lib
    C:/Setup/Perl/lib
    .

#!perl
use strict;
use warnings;
my $gross = -s "datei.txt" or die $!; 
print "Größe ist $gross\n";