Just add a bit of info on top of what Abigail-II said. If you my %stopper, it will stop the autovivification:

use Data::Dumper;
my %stopper;
$x = 'stopper';
exists $x->{'y'}->{'z'};
print Dumper $x;

print Dumper \%stopper;
[download]

Which prints:

$VAR1 = 'stopper';
$VAR1 = {};
[download]

Comment out that my %stopper line, you will see the autovivification:

$VAR1 = 'stopper';
$VAR1 = {
          'y' => {}
        };
[download]

If you my %stopper, it will stop the autovivification:

Well, that would be strange. Very, very strange. Do you think that happens because there's an explicite check in perl that says "hmmm, we are doing autovivification of a secondary key in the hash, but the parent hash is a lexical, so let's not do it", or that you've hit a strange bug?

Or could it be that autovivification is happening? And you are just giving the wrong argument to Dumper? Try giving \%{"stopper"} as argument to Dumper.

Abigail

Now that's interesting. Your post inspired me to dig a little deeper... it looks like the autovivification is still happening, but not on the lexical %stopper. Instead the global %::stopper is affected. Which makes sense, I suppose, because %::stopper is what was being affected in Abigail's original snippet, and with no lexical on scope, %stopper (i.e. the symbolic reference) was really referring to %::stopper. Very interesting, I certainly learned something. Thanks for pointing that out!

use Data::Dumper;
my %stopper;
$x = 'stopper';
exists $x->{'y'}->{'z'};
print Dumper $x;
print Dumper \%stopper;
print Dumper \%::stopper;
[download]

-- Mike

--
XML::Simpler does not require XML::Parser or a SAX parser. It does require File::Slurp.
-- grantm, perldoc XML::Simpler