Perl nuances: unnamed variable

Hello. Got an interesting question: what is $:: variable?

According to perldata there is no such special variable. According to perl variable syntax it's unnamed variable from main package. But if I dump %main:: - it's not there. But it's somewhere, because i can store and retrive data from it.

Read wonderful article about symbol tables but it didn't helped.

So, what is this thing?

And one more question: how several double-colon in a row being treated? Like $::::somevar ?

Comment on Perl nuances: unnamed variable

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identifiers that begin with digits, control characters, or punctuation char by LanX (Saint) on May 24, 2015 at 18:19 UTC
Special variables reserve all slots for their stash symbol i.e. all sigils are globally usable even if only `%main::` is meaningful. ( `%::` is only the abbreviation) Compare @a (better `@\|` ) or `%0` š (yes its a design flaw) Btw please start a new thread instead of just changing the title. Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Je suis Charlie!} edit (7 min) oops seems like they fixed it for `@a` `use warnings; use strict; %0 = (a=>1); @\| = (1..3); # @a =(1..3); # 'requires explicit package name' if uncommented` [download] update see also Scalar followed by parenthetical... and Why did @$ variable bite me in the ass? And here the reason why @a works as expected from perlvar: `Perl identifiers that begin with digits, control characters, or punctu +ation characters are exempt from the effects of the package declarati +on and are always forced to be in package main ; they are also exempt + from strict 'vars' errors. A few other names are also exempt in thes +e ways: ENV STDIN INC STDOUT ARGV STDERR ARGVOUT SIG` [download]	[reply] [d/l] [select]

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identifiers that begin with digits, control characters, or punctuation char
by LanX (Saint) on May 24, 2015 at 18:19 UTC

%main::

%::

Compare @a (better @| ) or %0 š

(yes its a design flaw)

Btw please start a new thread instead of just changing the title.

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)

Je suis Charlie!}

edit (7 min)

oops seems like they fixed it for @a

use warnings;
use strict;

%0 = (a=>1);
@| = (1..3);

# @a =(1..3);  #  'requires explicit package name'  if uncommented
[download]

update

And here the reason why @a works as expected

from perlvar:

Perl identifiers that begin with digits, control characters, or punctu
+ation characters are exempt from the effects of the package declarati
+on and are always forced to be in package main ; they are also exempt
+ from strict 'vars' errors. A few other names are also exempt in thes
+e ways:

        ENV      STDIN
        INC      STDOUT
        ARGV     STDERR
        ARGVOUT
        SIG
[download]

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