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;
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