Can't modify constant item in undef operator at -e line 1, near "b
+ =>"
    Execution of -e aborted due to compilation errors.
[download]

Abigail

Hmmm, undef is a function too, so I guess it's parsed as:

$x = {
    a     => undef('b') => 'x',
};
[download]

Which means you're asking Perl to undefine a string literal - still shouldn't segfault.

The error arises on 5.6.1, and running it through B::Deparse gives further wierdness:

Can't locate object method "pp_anonhash" via package "B::Deparse" (per
+haps you forgot to load "B::Deparse"?) at /usr/local/lib/perl5/5.6.1/
+sun4-solaris/B/Deparse.pm line 410.
CHECK failed--call queue aborted.
Segmentation Fault
[download]

$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]

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]

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.

You're right - I should have included version information right away. Here it is, just for the sake of completeness (because my question has been answered already): I'm running perl 5.6.1 under RedHat linux.

And here's the perl -V dump:

Summary of my perl5 (revision 5.0 version 6 subversion 1) configuratio
+n:
  Platform:
    osname=linux, osvers=2.4.9, archname=i686-linux
    uname='linux zeus.sail-labs.at 2.4.9 #5 smp tue aug 28 15:24:44 ce
+st 2001 i686 unknown '
    config_args=''
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef usemultipl
+icity=undef
    useperlio=undef d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
  Compiler:
    cc='cc', ccflags ='-fno-strict-aliasing -I/usr/local/include -D_LA
+RGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2',
    cppflags='-fno-strict-aliasing -I/usr/local/include'
    ccversion='', gccversion='2.96 20000731 (Red Hat Linux 7.1 2.96-81
+)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=1
+2
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
+ lseeksize=8
    alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -lndbm -lgdbm -ldl -lm -lc -lcrypt -lutil
    perllibs=-lnsl -ldl -lm -lc -lcrypt -lutil
    libc=/lib/libc-2.2.2.so, so=so, useshrplib=false, libperl=libperl.
+a
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynami
+c'
    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 Sep  3 2001 21:32:42
  %ENV:
    PERL5LIB=".:/home/robert/:/rnr/rnr_tools/:/rnr/rnr_train/bin/"
    PERLLIB="/home/robert/:/rnr/rnr_tools/:/rnr/rnr_train/bin/"
    PERLTEST_ROOT="/home/robert/start/perltest"
    PERL_MODLIB="/home/robert/:/home/robert/:/home/robert/:/rnr/rnr_to
+ols"
  @INC:
    .
    /home/robert/
    /rnr/rnr_tools/
    /rnr/rnr_train/bin/
    /usr/lib/perl5/5.6.1/i686-linux
    /usr/lib/perl5/5.6.1
    /usr/lib/perl5/site_perl/5.6.1/i686-linux
    /usr/lib/perl5/site_perl/5.6.1
    /usr/lib/perl5/site_perl/5.6.0
    /usr/lib/perl5/site_perl
[download]

pike