In op.c there is specific code to allow for keys( bareword ) to be treated as keys( %bareword ). If you turn on warnings you will get: Hash %bareword missing the % in argument 1 of keys() which is how I found the code:

        case OA_HVREF:
            if (kid->op_type == OP_CONST &&
                (kid->op_private & OPpCONST_BARE))
            {
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Add to this the long-standing habit of print( hello ) being the same as print( "hello" ) (other than the optional errors and warnings).

Add to that a patch that noted that Module->Method() can sometimes be interpretted as Module()->Method() (or was it only Method Module that had that problem?) and that added support for the syntax Module::->Method() (or was it Method Module::?). I suspect that this is what made print( hello:: ) the same as print( "hello" ).

So these (may) explain why keys( main ) and keys( main:: ) are the same as keys( %main ).

Also consider that %main:: didn't use to work. You used to have to do %{"main::"}. And print( :: ) is the same as print( "::" ). So it makes some quirky sense that keys( :: ) is the same as keys( %:: ) which is now the same as keys( %{"main::"} ).

push me, harder;
pop goes_the_weasel;
shift yeyes;
# etc.
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_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area)
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

(keys ::) is the same as (keys %::) is the same as (keys %main::).
main:: is a scalar that contains the value main.

Just don't ask me why! Once again, I'm stumped!

I had hoped that Data::Dumper might shed some light on it but so far it hasn't.

perl -MO=Deparse -e"print join qq(\n), keys main::::::"
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turns into %::. However, using %:: turns into %main:: internally.

a little bit more explaination:
in main::::, the first set of :: is the operator, when the second set of :: is a val.

You keep coming up with these cool questions so would you care to share what you are working on?

Well, I'm just trying to look busy.

Seriously, I came up with this one when checking out attributes::bootstrap after reading tye's reply. My one-liner printed main's contents instead! Blame the shell for thinking %attributes was an environment variable, so it saw :: alone. Since %'s are a constant problem on the command line, I thought "oh, I can even leave it off when the context must be a hash?" just like the @ in the push in old versions of Perl. Well, it's inconsistant.

For the others, deep symbol table and ref stuff, I'm working on Exporter::VA and generally trying to understand everything.

—John