[Phoenix-pm] Eval Namespace Question

[Douglas E. Miles]

Bill Nash wrote:

>
> If you're excited about perl forwarding that namespace into your eval, 
> just remember that's a double edged sword. When you're to a point 
> where you're thinking about efficiency, or perl starts to core dump 
> with frightening regularity, revisit your use of eval.
>
> - billn
>
Well, actually I've been using the code for several years now.  No core 
dumps.  I just had reason to look at it again, realized what was 
happening, and wondered how it worked.

> On Mon, 7 Aug 2006, Douglas E. Miles wrote:
>
>> Hey all!
>>
>> I'm having fun hacking Perl for a change, and I just realized I'd been
>> using a feature that I don't completely understand.  man perlfunc says
>> this about eval:
>>
>> In the first form, the return value of EXPR is parsed and exe-
>> cuted as if it were a little Perl program.  The value of the
>> expression (which is itself determined within scalar context)
>> is first parsed, and if there weren't any errors, executed in
>> the lexical context of the current Perl program, so that any
>> variable settings or subroutine and format definitions remain
>> afterwards.
>>
>> This means that in my code below, that $bar is in scope within the
>> eval.  What blows me away is that $foo::foo is also in scope because of
>> the "package foo" statement in $eval_string.  Does anyone know how perl
>> accesses both namespaces simultaneously without specifying the namespace
>> in each variable name.  Feel free to laugh at me if I'm missing
>> something basic. :)  The cool thing is that this behavior is exactly
>> what I need.  I'd just like to understand how it works (and hope that it
>> isn't a misfeature that might be removed in the future).  Thanks!
>>
>>
>> #!/usr/bin/perl
>>
>> package foo;
>>
>> $foo = "FOO!";
>>
>> package bar;
>>
>> my $bar = "BAR!";
>>
>> my $perl_code = 'print "$bar $foo\n"';
>> print "$perl_code\n";
>>
>> my $eval_string = "package foo;\n$perl_code";
>> eval $eval_string;
>>
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