Re^2: Autovivification sucking the life out of me

[shenme]

But I am not explicitly telling Perl to autovivify, rather I am (intending to) just reference the values, in this case using a slice.

Refer to my simpler example above. Using see_args( @foo{qw(BAR BAZ)} ); causes result:

at start: BAR '<absent>'
at end: BAR '<undef>'

But changing that to see_args( $foo{BAR}, $foo{BAZ} ); results in:

at start: BAR '<absent>'
at end: BAR '<absent>'

This is most perplexing to me.

[Skeeve]

Tell you what: It's perplexing to me the other way around!

Until 2 days ago I thought something like
if ($foo{'BAR'}) ...
would already vivify that hash entry.

But then I learned in the Chatter Box that it doesn't in perl 5.8 (or maybe a bit earlier).

And now I did a test. Compare the output

use Data::Dumper;
%foo=(BAZ=>1);
print Dumper \%foo if $foo{BAR} || 1;
print Dumper \%foo if @foo{BAR,BAZ} || 1;

Output:

$VAR1 = {
          'BAZ' => 1
        };
$VAR1 = {
          'BAZ' => 1
        };



use Data::Dumper;
%foo=(BAZ=>1);
print Dumper \%foo if call($foo{BAR});
print Dumper \%foo if call(@foo{BAR,BAZ});
sub call { return 1 }

Output:

$VAR1 = {
          'BAZ' => 1
        };
$VAR1 = {
          'BAR' => undef,
          'BAZ' => 1
        };


So it's really the fact that the slice is used in a subroutine call. When you replace call with print, autovivification does not happen

So now I ask myself: Is there a bug and you are certified bugfinder!? ;-)