${ *{${ns} . '::foo'} } = $cram;
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You could also write

${ $::{$ns.'::'}{foo} } = $cram;
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in which case you wouldn't need the no strict 'refs'.

#!/usr/bin/perl -l
use strict;
use warnings;

my $ns = 'Teddy::';

${ $::{$ns}{foo} } = 'cheese';
print '$Teddy::foo: ', $Teddy::foo;

# or the other way round
$Teddy::foo = 'bar';
print '${ $::{$ns}{foo} }: ', ${ $::{$ns}{foo} };

__END__
$Teddy::foo: cheese
${ $::{$ns}{foo} }: bar
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The main stash %:: holds an entry 'Teddy::', whose value is the stash of that package (or more precisely, a glob whose hash part is the stash).  The latter holds an entry 'foo', whose value is a glob, the scalar slot of which you can select with ${ ... }

print grep /Teddy/, keys %::;    # Teddy:: 
print $::{'Teddy::'};            # *main::Teddy::
print keys %{$::{'Teddy::'}};    # foo
print $::{'Teddy::'}{foo};       # *Teddy::foo
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P.S.: you could also put a direct reference to a string 'cheese' in the scalar slot of the glob, in which case you would get a kind of read-only variable:

$::{'Teddy::'}{foo} = \'cheese';

print $Teddy::foo;    # cheese
$Teddy::foo = 'bar';  # "Modification of a read-only value attempted a
+t ..."
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Your code is, I admit, more clever than mine. But if I understand correctly, you're setting up a hash in the stasher's symbol table. Since my case isn't really a script, that's not main and I might write something like:

package Stasher; 

sub stash {
    my $ns = caller;
    $ns    = $ns . '::';
    ${ $Stasher::{$ns}{foo} } = 'cheese';
};
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Before I hammered out my current approach, I considered a less clever one:

package Stasher; 
our %stash_of;

sub stash {
    my $ns = caller;
    $stash_of{$ns}{foo} = 'cheese';
};
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This resembles a flyweight object and suffers from a similar weakness, in that Stasher keeps %stash_of entries alive unless and until an explict DESTROY is called. That's okay for flyweights but in my case, how does Stasher know when caller's entire package has gone out of scope?

My thought was to stash $foo in caller's symbol table because I can rely on it being deallocated in Perl's own good time.

- the lyf so short, the craft so long to lerne -

But if I understand correctly, you're setting up a hash in the stasher's symbol table. Since my case isn't really a script, that's not main ...

Not really sure what you mean.  Of course, the approach isn't limited to main — the latter is just the top-level stash that every "package path" is rooted at.

Essentially, all I wanted to point out is that, in general

    ${ $::{'PackageA::'}{'PackageB::'}{'PackageC::'}{foo} }
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functionally achieves the same as your symbolic reference

    ${ *{"PackageA::PackageB::PackageC::foo"} }
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(which could be simplified to  ${"PackageA::PackageB::PackageC::foo"},  btw — or ${"$ns\::foo"} in your specific case)

But, as the former approach doesn't involve symbolic references, it's compatible with use strict, i.e. it doesn't need no strict 'refs'.


P.S.: in several places of the current version of your original node, you're missing the closing curly in the expression ${ *{"${ns}\::foo"}

... after which both strict and warnings should be re-enabled.

The assignment doesn't produce any warnings. It's the later use of the variable that does. Note that this warning can be avoided if the variable is created at compile time from a different package than the one in which it resides. (See vars.)

As for strict, you can let Perl re-enable strict by placing the no strict 'refs'; inside of curlies.

$ perl -le'
   use strict;
   use warnings;
   BEGIN {
      my $pkg = "Foo::Bar";
      my $var = "s";
      no strict "refs";
      ${"${pkg}::$var"} = 123;
   }
   print $Foo::Bar::s;
'
123
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