findnode() results in Invalid Expression only on non-self-compiled perl

Hello,

I'm a bit new to perl, but I think I'm experiencing a very strange  
behavior in perl.
findnodes() gives me an Invalid expression only on perl which comes  
with the distribution on SuSE 10.3, RHEL4 and RHEL 5.1.

But if I compile the entire perl by myself it doesnt occur and works  
just find.
I tried with different versions of perl and XML-Lib but no difference.

Here is the code:

#!/usr/bin/perl -w
use strict;
use XML::LibXML;
use Getopt::Std;
use vars qw/$opt_x/;

{ # main

my $parser = XML::LibXML->new();
my $usercfg = $parser->parse_file('./user.cfg');
my $mailcfg = $parser->parse_file('./server.cfg');
my $uroot   = $usercfg->documentElement;
my $mroot   = $mailcfg->documentElement;

my @unodes      = $uroot->findnodes('./');
my @mnodes      = $mroot->findnodes('./');


The different config show this:
/usr/bin/perl -V (Distribution:

Summary of my perl5 (revision 5 version 8 subversion 5) configuration:
  Platform:
    osname=linux, osvers=2.6.9-55.0.9.elsmp, archname=i386-linux- 
thread-multi
    uname='linux hs20-bc1-5.build.redhat.com 2.6.9-55.0.9.elsmp #1 smp  
tue sep 25 02:16:15 edt 2007 i686 i686 i386 gnulinux '
    config_args='-des -Doptimize=-O2 -g -pipe -m32 -march=i386 - 
mtune=pentium4 -Dversion=5.8.5 -Dmyhostname=localhost - 
Dperladmin=root@localhost -Dcc=gcc -Dcf_by=Red Hat, Inc. - 
Dinstallprefix=/usr -Dprefix=/usr -Darchname=i386-linux - 
Dvendorprefix=/usr -Dsiteprefix=/usr -Duseshrplib -Dusethreads - 
Duseithreads -Duselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db - 
Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio - 
Dinstallusrbinperl -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less  
-isr -Dinc_version_list=5.8.4 5.8.3 5.8.2 5.8.1 5.8.0'
    hint=recommended, useposix=true, d_sigaction=define
    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='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBUGGING -fno- 
strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE - 
D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
    optimize='-O2 -g -pipe -m32 -march=i386 -mtune=pentium4',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBUGGING -fno-strict- 
aliasing -pipe -I/usr/local/include -I/usr/include/gdbm'
    ccversion='', gccversion='3.4.6 20060404 (Red Hat 3.4.6-8)',  
gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',  
lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='gcc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread - 
lc
    perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=/lib/libc-2.3.4.so, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.3.4'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E - 
Wl,-rpath,/usr/lib/perl5/5.8.5/i386-linux-thread-multi/CORE'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'


Characteristics of this binary (from libperl):
  Compile-time options: DEBUGGING MULTIPLICITY USE_ITHREADS  
USE_LARGE_FILES PERL_IMPLICIT_CONTEXT
  Built under linux
  Compiled at Oct 22 2007 16:12:50


/usr/local/bin/perl -V (self compiled)
Summary of my perl5 (revision 5 version 8 subversion 7) configuration:
  Platform:
    osname=linux, osvers=2.6.9-42.0.3.elsmp, archname=i686-linux
    uname='linux pony.cenix-bioscience.com 2.6.9-42.0.3.elsmp #1 smp  
mon sep 25 17:28:02 edt 2006 i686 athlon i386 gnulinux '
    config_args=''
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef  
usemultiplicity=undef
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fno-strict-aliasing -pipe -I/usr/local/include  
-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
    optimize='-O2',
    cppflags='-fno-strict-aliasing -pipe -I/usr/local/include -I/usr/ 
include/gdbm'
    ccversion='', gccversion='3.4.6 20060404 (Red Hat 3.4.6-3)',  
gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',  
lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
    libc=/lib/libc-2.3.4.so, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.3.4'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'


Characteristics of this binary (from libperl):
  Compile-time options: USE_LARGE_FILES
  Built under linux
  Compiled at Oct 11 2006 02:59:09

It would be great if someone could pojnt me in the right direction. I  
would like to use the script on several machines and therefore dont  
like to compile perl everytime.