Works fine for me.

$x = {
    a     => undef
    b     => 'x',
};
__END__
Can't modify constant item in undef operator at - line 3, near "b     
+=>"
Execution of - aborted due to compilation errors.
[download]

Even Abigail failed to provide a perl -V dump

Summary of my perl5 (revision 5 version 6 subversion 1) configuration:
  Platform:
    osname=MSWin32, osvers=4.0, archname=MSWin32-x86-multi-thread
    uname=''
    config_args='undef'
    hint=recommended, useposix=true, d_sigaction=undef
    usethreads=undef use5005threads=undef useithreads=define usemultip
+licity=define
    useperlio=undef d_sfio=undef uselargefiles=undef usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
  Compiler:
    cc='cl', ccflags ='-nologo -O1 -MD -DNDEBUG -DWIN32 -D_CONSOLE -DN
+O_STRICT -DHAVE_DES_FCRYPT  -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_S
+Y
S -DPERL_MSVCRT_READFIX',
    optimize='-O1 -MD -DNDEBUG',
    cppflags='-DWIN32'
    ccversion='', gccversion='', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=10
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
+ lseeksize=4
    alignbytes=8, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='link', ldflags ='-nologo -nodefaultlib -release  -libpath:"C:/
+Perl\lib\CORE"  -machine:x86'
    libpth="C:\Program Files\Microsoft Visual Studio\VC98\mfc\lib" "C:
+\Program Files\Microsoft Visual Studio\VC98\lib" "C:\Perl\lib\CORE"
    libs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib
+  comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib  netap
+i
32.lib uuid.lib wsock32.lib mpr.lib winmm.lib  version.lib odbc32.lib 
+odbccp32.lib msvcrt.lib
    perllibs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool
+.lib  comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib  n
+e
tapi32.lib uuid.lib wsock32.lib mpr.lib winmm.lib  version.lib odbc32.
+lib odbccp32.lib msvcrt.lib
    libc=msvcrt.lib, so=dll, useshrplib=yes, libperl=perl56.lib
  Dynamic Linking:
    dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -release  -l
+ibpath:"C:/Perl\lib\CORE"  -machine:x86'


Characteristics of this binary (from libperl):
  Compile-time options: MULTIPLICITY USE_ITHREADS PERL_IMPLICIT_CONTEX
+T PERL_IMPLICIT_SYS
  Locally applied patches:
        ActivePerl Build 633
  Built under MSWin32
  Compiled at Jun 17 2002 21:33:05
  @INC:
    C:/Perl/lib
    C:/Perl/site/lib
    .
[download]

I get the same thing with perl 5.8. I don't see how this is a segfault.

MJD says you can't just make shit up and expect the computer to know what you mean, retardo! ** The Third rule of perl club is a statement of fact: pod is sexy.