[perl #133155] perl5: false warning on "Multidimensional syntax notsupported"

# New Ticket Created by  Wolf-Dietrich Moeller 
# Please include the string:  [perl #133155]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=133155 >


Hi,
I found a false warning on "Multidimensional syntax".
The test program below is executed correctly, but line 7
triggers a false warning. This is surprising, as the other
'print' lines have a similar structure without raising this
warning. Why should this be raised here? From the syntax it
is clear that both variables are parameters of "index", as
it has (at least) two arguments.

Best regards
Wolf

### Start test program 'test_index.pl' ###
use warnings;
my @x = (['a','b']);
my @y = ('a','b');
my $z = 'rst';
my $i = 's';
print ' 6: ',$x[0][index $z,$i],"\n";
print ' 7: ',$y[index $z,$i],"\n";
print ' 8: ',$y[index($z,$i)],"\n";
print ' 9: ',$y[index 'rst',$i],"\n";
print '10: ',@y[index $z,$i],"\n";
### end test program ###

Output:
Multidimensional syntax $y[index $z,$i] not supported at test_index.pl line
7.
 6: b
 7: b
 8: b
 9: b
10: b

-----------------------------------------------------------------
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.26.2:

Configured by strawberry-perl at Sun Apr 15 11:47:59 2018.

Summary of my perl5 (revision 5 version 26 subversion 2) configuration:
   
  Platform:
    osname=MSWin32
    osvers=10.0.16299.371
    archname=MSWin32-x86-multi-thread-64int
    uname='Win32 strawberry-perl 5.26.2.1 #1 Sun Apr 15 11:47:13 2018 i386'
    config_args='undef'
    hint=recommended
    useposix=true
    d_sigaction=undef
    useithreads=define
    usemultiplicity=define
    use64bitint=define
    use64bitall=undef
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
    bincompat5005=undef
  Compiler:
    cc='gcc'
    ccflags =' -s -O2 -DWIN32 -D__USE_MINGW_ANSI_STDIO
-DPERL_TEXTMODE_SCRIPTS -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS
-DUSE_PERLIO -fwrapv -fno-strict-aliasing -mms-bitfields'
    optimize='-s -O2'
    cppflags='-DWIN32'
    ccversion=''
    gccversion='7.1.0'
    gccosandvers=''
    intsize=4
    longsize=4
    ptrsize=4
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=12
    longdblkind=3
    ivtype='long long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='long long'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='g++'
    ldflags ='-s -L"C:\Perl\perl\lib\CORE" -L"C:\Perl\c\lib"'
    libpth=C:\Perl\c\lib C:\Perl\c\i686-w64-mingw32\lib
C:\Perl\c\lib\gcc\i686-w64-mingw32\7.1.0
    libs= -lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32
-ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr
-lwinmm -lversion -lodbc32 -lodbccp32 -lcomctl32
    perllibs= -lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32
-ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr
-lwinmm -lversion -lodbc32 -lodbccp32 -lcomctl32
    libc=
    so=dll
    useshrplib=true
    libperl=libperl526.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_win32.xs
    dlext=xs.dll
    d_dlsymun=undef
    ccdlflags=' '
    cccdlflags=' '
    lddlflags='-mdll -s -L"C:\Perl\perl\lib\CORE" -L"C:\Perl\c\lib"'


---
@INC for perl 5.26.2:
    C:/Perl/perl/site/lib
    C:/Perl/perl/vendor/lib
    C:/Perl/perl/lib

---
Environment for perl 5.26.2:
    HOME (unset)
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=...
    PERL_BADLANG (unset)
    SHELL (unset)

• [perl #133155] perl5: false warning on "Multidimensional syntax notsupported" by Wolf-Dietrich Moeller