in reply to symbol/glob hash explanation

Where can I find the gory details of this construct used by glob/symbol-based modules

See Typeglobs and Filehandles in perldata.

Is there another way to access that hash?

If $sym contains 'fred', then ${*$sym}{hash_key} = 'something'; is equivalent to $fred{hash_key} = 'something';.

Or strictly:

our %fred;

$fred{hash_key} = 'something';

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I can't find the equivalent of the STDIN example. Where is it stored? Is it a hash that's magically not accessible by name?

There is a hash (and array and scalar et al.) associated with the STDIN glob:

c:\test>perl -E"${*STDIN}{fred} = 'bill'; say $STDIN{fred}"
bill

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they just aren't normally used for anything.

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"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

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Re^2: symbol/glob hash explanation
by rwstauner (Acolyte) on May 03, 2011 at 04:36 UTC

    right, I understand those examples, but what about when $sym is *Symbol::GEN0 ?

    Is that hash "hidden" because it's not a simple name?

      DB<2> x $s = Symbol::gensym
0  GLOB(0x96f82b8)
   -> *Symbol::GEN0
  DB<3> x ${*$s}{goo} = 'ber'
0  'ber'
*  DB<4> x \%{*$s}
0  HASH(0x96f82e8)
   'goo' => 'ber'
  DB<5> x *$s
0  *Symbol::GEN0
  DB<6> x $s
0  GLOB(0x96f82b8)
   -> *Symbol::GEN0
  DB<7> x $Symbol::GEN0{goo}
0  undef
*  DB<8> x \%Symbol::GEN0
0  HASH(0x97783c0)
     empty hash
*  DB<9> x \%{Symbol::GEN0}
0  HASH(0x97783c0)
     empty hash
*  DB<10> x \%{*Symbol::GEN0}
0  HASH(0x97783c0)
     empty hash
*  DB<11> x \%{"Symbol::GEN0"}
0  HASH(0x97783c0)
     empty hash

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    I've tried various ways of using the reference address and haven't found anything either.

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[d/l]
      I've tried various ways of using the reference address

      All except the right one :)

      You already did x ${*$s}{goo} = 'ber' and x *$s -> *Symbol::GEN0

      So try:x ${*Symbol::GEN0}{goo}

      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
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[d/l]
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        I did try that and it does not work, at least not on my 5.10.1

          DB<2> $s = Symbol::gensym

  DB<3> x ${*$s}{goo} = 'ber'
0  'ber'
*  DB<4> x \%{*$s}{goo}
syntax error at (eval 8)[/usr/share/perl/5.10/perl5db.pl:638] line 2, 
+near "}{goo"
*  DB<5> x \%{*$s}
0  HASH(0x86285e8)
   'goo' => 'ber'
*  DB<6> x \%{*Symbol::GEN0}
0  HASH(0x87144e0)
     empty hash
*  DB<7> x ${*Symbol::GEN0}{goo}
0  undef
  DB<8> x $]
0  5.010001
  DB<9> x $s
0  GLOB(0x86285b8)
   -> *Symbol::GEN0

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        ...

        *  DB<8> x \%{*Symbol::GEN0}
0  HASH(0x8aab260)
     empty hash
*  DB<9> x \%{*{Symbol::GEN0}}
0  HASH(0x8aab260)
     empty hash
*  DB<10> x \%{*{*Symbol::GEN0}}
0  HASH(0x8aab260)
     empty hash
*  DB<11> x \%{'' . *$s}
0  HASH(0x8aab260)
     empty hash
*  DB<12> x \%{*$s}
0  HASH(0x8a5b5e8)
   'goo' => 'ber'
*  DB<13> use Scalar::Util qw(refaddr)

  DB<14> x \%{*refaddr($s)}
syntax error at (eval 20)[/usr/share/perl/5.10/perl5db.pl:638] line 2,
+ near "*refaddr("
*  DB<15> x \%{refaddr($s)}
0  HASH(0x8b6eea0)
     empty hash
*  DB<16> x \%{sprintf "%x", refaddr($s)}
0  HASH(0x8b73ef0)
     empty hash
*  DB<17> x \%{*{"$s"}}
0  HASH(0x8b73c10)
     empty hash

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        It does not show up when I dump \%:: (or \%Symbol or \%Symbol:: or \%Symbol::GEN0 or \%Symbol::GEN0:: either (excluded for brevity) at least not that i can see.

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[d/l]
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