what are the lowercase qw/stderr stdin stdout/ for

What do the _<-ones mean

precisely when and where the destructor is used

Dave.

A better subject would be something similar to: 'Symbol table of the main-package'...

Update: I should have know that mentioning that %:: is the symbol table of the package main and that it therefor is a better title would get downvoted....
Noone cares how it is called right?

Now I really wonder why I stopped posting a few months ago...

Update: I should have know that mentioning that %:: is the symbol table of the package main and that it therefor is a better title would get downvoted.... Noone cares how it is called right?

FWIW it wasn't me to downvote you, if not for anything else because I don't have votes left for today...

I think you got downvoted because you only made a cmt about the subject with no positive content re the actual question. I say so because something similar happened to me in the past. We may both dislike this kind of things but this is a community after all, so we have to accept its rules if we like to take part to it...

'tisn't a rule.

No but there are better ways of indicating that the subject should be changed like "considering" the node or messaging the author. That's why I downvoted it.

/J\

Animator isn't allowed to consider a node

This is actually the root of the symbol table, isn't it? You might notice that 'main::' is included in the listings everyone posted.

mhoward - at - hattmoward.org

bash-2.03$ perl -le 'print for sort keys %::'

CYGWIN_NT-5.1                   Solaris             
==============                  ======= 
                                                              
"                               "            
$                               $            
+                               +             
-                               -             
/                               /             
0                               0             
<none>::                        <none>::      
@                               @             
ARGV                            ARGV          
CORE::                          CORE::        
Cwd::                           DB::          
DB::                            DynaLoader::  
DynaLoader::                    ENV           
ENV                             INC           
INC                             IO::          
IO::                            Internals::   
Internals::                     PerlIO::      
PerlIO::                        Regexp::      
Regexp::                        STDERR        
STDERR                          STDIN         
STDIN                           STDOUT        
STDOUT                          UNIVERSAL::   
UNIVERSAL::                     _             
Win32::                         _<-e          
Win32CORE::                     _<perlio.c       
_                               _<perlmain.c 
_<Win32CORE.c                   _<universal.c
_<cygwin.c                      _<xsutils.c  
_<perlio.c                      attributes:: 
_<perlmain.c                    main::       
_<universal.c                   stderr       
_<xsutils.c                     stdin        
attributes::                    stdout       
main::                          utf8::       
stderr                          
stdin                           
stdout                                 
utf8::
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/
stderr
_<.\win32.c
_<perllib.c
utf8::
"
CORE::
DynaLoader::
stdout
attributes::

stdin
ARGV
INC
ENV
Regexp::
_<..\perlio.c
UNIVERSAL::
$
main::
-
Win32::
PerlIO::
_<..\universal.c
0

@
_<..\xsutils.c
STDOUT
IO::

_
+
STDERR
Internals::
STDIN
DB::
<none>::
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# on cygwin

perl -e 'print "$_ => $::{$_}\n" for keys %::'

__OUTPUT__

/ => *main::/
stderr => *main::stderr
_<.\win32.c => *main::_<.\win32.c
_<perllib.c => *main::_<perllib.c
utf8:: => *main::utf8::
" => *main::"
CORE:: => *main::CORE::
DynaLoader:: => *main::DynaLoader::
stdout => *main::stdout
attributes:: => *main::attributes::
&#8597; => *main::&#8597;
stdin => *main::stdin
ARGV => *main::ARGV
INC => *main::INC
ENV => *main::ENV
Regexp:: => *main::Regexp::
_<..\perlio.c => *main::_<..\perlio.c
UNIVERSAL:: => *main::UNIVERSAL::
$ => *main::$
main:: => *main::main::
- => *main::-
Win32:: => *main::Win32::
PerlIO:: => *main::PerlIO::
_<..\universal.c => *main::_<..\universal.c
0 => *main::0
 => *main::
@ => *main::@
_<..\xsutils.c => *main::_<..\xsutils.c
STDOUT => *main::STDOUT
IO:: => *main::IO::
&#8593; => *main::&#8593;
_ => *main::_
+ => *main::+
STDERR => *main::STDERR
Internals:: => *main::Internals::
STDIN => *main::STDIN
DB:: => *main::DB::
<none>:: => *main::<none>::
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See broquaint's excellent node Of Symbol Tables and Globs.

fixed link

Thank you blazar, johnnywang and broquaint for an excellent education on the Perl symbol space.

---

s//----->\t/;$~="JAPH";s//\r<$~~/;{s|~$~-|-~$~|||s |-$~~|$~~-|||s,<$~~,<~$~,,s,~$~>,$~~>,, $|=1,select$,,$,,$,,1e-1;print;redo}

Yes... to see if something is a scalar you can do *something{SCALAR}. if it is a scalar then it will exists and it will be defined... (read `perldoc perlmod` if you need more information)

Or you could use the Devel::Symdump package...

I seem to recall that every glob has an SV in the scalar slot as an optimization, but I can't confirm it by reading the source code. (I'm not sure I've even found the right spot in the code.)

Is there anyway to find out what the typeglobs really are? (i.e, its scalar value, array value, etc.)

Each slot in the GLOB, if defined, contains a reference to the actual value. The following works for looking up scalars, arrays, and hashes:

for my $g(sort keys %::) { 
  print "$g:\n"; 
  if(defined( *{$g}{SCALAR} ) ) { 
    print "  SCALAR: ", ${ *{$g}{SCALAR} }, "\n"; 
  } 
  if(defined( *{$g}{ARRAY} ) ) { 
    print "  ARRAY: ", join ", ", @{ *{$g}{ARRAY} }, "\n"; 
  } 
  if(defined( *{$g}{HASH}  ) ) { 
    print "  HASH: "; 
    while(my ($k, $v) = each %{ *{$g}{HASH} } ) { 
      print "$k => $v, " 
    } 
  } 
  print "\n" 
}
[download]

I have improved this script a bit, it can recurse into symbol tables now.
I learned something new today. Internals::SvREADONLY can reset the readonly flag :)

my $table=shift||'';
$table.="::";

dumptable($table);

sub dumptable{
my $table=shift;
my $indent=shift||'';
while (my ($key,$value)=each %$table ){
    print qq!$indent"$key":\n!;
    if(defined(*{$value}{SCALAR}) and defined(${ *{$value}{SCALAR}})){
        print "$indent\tSCALAR: ",${*{$value}{SCALAR}}, "\n";
    }
    if(defined( *{$value}{ARRAY} ) ) {
        print "$indent\tARRAY: ", join ", ",@{*{$value}{ARRAY}}, "\n";
    }
    if(defined( *{$value}{HASH}  ) ) {
        if ($key =~ /::$/){
            print "$indent\tSYMTAB:\n";
            dumptable($value,"\t".$indent)
                if (*{$value}{NAME} ne "main::");
        }else{
            print "\tHASH:\n";
            while(my ($k, $v) = each %{ *{$value}{HASH} } ) {
                print "$indent\t\t$k => $v,\n"
            }
        }
    }
    if(defined( *{$value}{CODE}  ) ) {
        print "$indent\tCODE: ",*{$value}{CODE},"\n";
    };
    if(defined( *{$value}{IO}  ) ) {
        print "$indent\tIO: ",*{$value}{IO},"\n";
    };
    print "\n"
}
}
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