site/perl directory is missing in perl #INC search path - perl

Question

I am developing a bunch of Perl scripts for my workmates and me.
To ease distribution, Perl itself resides on a network path and is used from there directly using this header:
#rem = '--*-Perl-*--
#echo off
\\network\path\to\Perl\bin\perl.exe -x -S %0 %*
goto EndOfPerl
#rem ';
#!perl
#line 8
#####################################################################
This worked fine (and still does!), but a collegue needed a standalone version, so we copied the complete network installation of Perl to the local hard disk.
After changing the header to use the local location we get the message:
Can't locate Tk.pm in #INC (#INC contains: C:/tools/Perl/5.16.1/lib .) at Test.cmd line 30
Now I always thought #INC was compiled into Perl. At least, it shouldn't change by simply copying Perl to another location.
There is a slight difference in Perl -V output when started locally.
Here is what I get when started from the network:
Summary of my perl5 (revision 5 version 16 subversion 1) configuration:
Platform:
osname=MSWin32, osvers=5.2, archname=MSWin32-x86-multi-thread
uname=''
config_args='undef'
hint=recommended, useposix=true, d_sigaction=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 -DPERL_TEXTMODE_SCRIPTS -DUSE_SITECUSTOMIZE -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -DUSE_PERLIO -D_USE_32BIT_TIME_T',
optimize='-MD -Zi -DNDEBUG -O1',
cppflags='-DWIN32'
ccversion='12.00.8168', 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:\Perl\lib\CORE" -machine:x86'
libpth=\lib
libs=oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib netapi32.lib uuid.lib ws2_32.lib mpr.lib
winmm.lib version.lib odbc32.lib odbccp32.lib comctl32.lib msvcrt.lib
perllibs=oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib netapi32.lib uuid.lib ws2_32.lib mpr.lib winmm.lib version.lib odbc32.lib odbccp32.lib comctl32.lib msvcrt.lib
libc=msvcrt.lib, so=dll, useshrplib=true, libperl=perl516.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:\Perl\lib\CORE" -machine:x86'
Characteristics of this binary (from libperl):
Compile-time options: HAS_TIMES HAVE_INTERP_INTERN MULTIPLICITY
PERLIO_LAYERS PERL_DONT_CREATE_GVSV
PERL_IMPLICIT_CONTEXT PERL_IMPLICIT_SYS
PERL_MALLOC_WRAP PERL_PRESERVE_IVUV PL_OP_SLAB_ALLOC
USE_ITHREADS USE_LARGE_FILES USE_LOCALE
USE_LOCALE_COLLATE USE_LOCALE_CTYPE
USE_LOCALE_NUMERIC USE_PERLIO USE_PERL_ATOF
USE_SITECUSTOMIZE
Locally applied patches:
ActivePerl Build 1601 [296175]
Built under MSWin32
Compiled at Aug 30 2012 20:08:55
#INC:
//network/path/to/Perl/site/lib
//network/path/to/Perl/Perl/lib
.
And here is the output when executed from the local drive:
<snip>
Compiled at Aug 30 2012 20:08:55
%ENV:
PERL_DIR="C:\tools\Perl\5.16.1"
#INC:
C:/tools/Perl/5.16.1/lib
.
The site/lib part is gone!
Any ideas, anyone?