in reply to creating a new symbol table glob

You're overworking the problem a bit, I think. 
package pkg;
print \*{"pkg::foo"};
{
  local %pkg::;
  print \*{"pkg::foo"};
}
print \*{"pkg::foo"};

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The only problem is that perl compiles in glob addresses when it knows them, so only symbolic references acknowledge the new glob address. For instance, try this: 
{ package pkg;
  local %pkg::;
  print \*{"pkg::foo"};
  print \*foo; }

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They *should* have the same address, but they don't since the address looked up at compile-time.

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Re: Re: creating a new symbol table glob
by ysth (Canon) on Nov 04, 2003 at 12:49 UTC
    Thanks, I think only something that does local %pkg:: is going to work. Putting everything else back in the local %pkg:: is the next step. Something like this (not yet tested): 
    my $opkg = \%pkg::;
local %pkg::;
$_ ne "foo" and *{"pkg::$_"}=$opkg->{$_} for keys %$opkg;

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    I can't decide if this is so hard because globs are such strange scalars or because symbol tables are such perfectly ordinary hashes.

    (About the compile-time lookup of globs, I remember once seeing a quote from Larry complaining about an optimization that made globals faster but not lexicals. Making every global reference look up the glob afresh sure would be a hearty encouragement to always use lexicals. :)

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[d/l]
      Hmm.......... 
      {
$foo::bar = "Show me";
print \*{"foo::bar"};
local %foo:: = %foo::;
print \*{"foo::bar"};
print ${"foo::bar"};   # runtime lookup
}

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      Looks like that's enough. Your big problem is that even changing the glob addresses has no effect in the rest of the program, since perl never looks up symbol-table entries at runtime unless you use a symbolic ref. There is very limited functionality to replacing the glob entries in the symbol-table, since you must use it like a hash in order to see the effect.
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[d/l]
        That was me, btw. I forgot to login. Your question was very interesting... I did alot of testing to see how Perl reacts to stash changes like that. Fun and challenging question.
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