Re: Dereferencing a reference to a typeglob? [Postfix Dereference Syntax]

[kcott]

"...use v5.24;..."

"Dereferencing a reference to a typeglob" can be done with Postfix Dereference Syntax (i.e. $globref->**). Some examples:

$ perl -v | head -2 | tail -1
This is perl 5, version 24, subversion 0 (v5.24.0) built for darwin-th
+read-multi-2level
$ alias perle
alias perle='perl -Mstrict -Mwarnings -Mautodie=:all -E'
$ perle 'use 5.024; my $x = \*STDERR; say "OUT"; say { $x->** } "ERR"'
OUT
ERR
$ perle 'use 5.024; my $x = \*STDERR; say "OUT"; say { $x->** } "ERR"'
+ > /dev/null
ERR
$ perle 'use 5.024; my $x = \*STDERR; say "OUT"; say { $x->** } "ERR"'
+ 2> /dev/null
OUT
$

I wrote a fair amount about using this syntax in general, just yesterday: "Re^3: Syntax Question Related to "join" on a Complex Data Structure [postderef and postderef_qq]". You'll find examples of "$arrayref->@*", which may be closer (than "$globref->**") to the type of thing you're after.

[stevieb]

++, but this doesn't solve the OP's problem of derefing a lexical, it acts the same way as a normal deref does (unless I'm missing something):

perl -E 'my $a=25; my $x=\*a; say $x->**; say $$x;'
*main::a
*main::a

[LanX]

> perl -E 'my $a=25; my $x=\*a; ... '

This code doesn't do what you think it does.

*a is always addressing the typeglob of the global symbol(s) named a , i.e. &a, $a, @a, %a the filehandle a and the format a .

( see here for how to use the clearer {SLOT} syntax.)

Maybe this code example makes it clearer:

  DB<104> $a=42; my $a=666; my $ra=\*a; print $$$ra
42

update

Best think of the STASH (= Symbol Table Hash) as a Hash of Hashes, where the second level "hash" is a special structure called "glob" which always has exactly 6 fixed entries, which are either undef or a reference.

Lexicals use a totally different mechanism in the so called "Pad" and can't be addressed with * because there is nothing like a "lexical glob" unifying all lexical symbols.

If you use PadWalker to introspect pads you'll see that $x', '%x', '@x listed as separate top level symbols.

[kcott]

See my "Postfix Dereference Chaining" solution.