If you need to test for existence without autovivification, you'll have to code up a test that goes something like this:

sub my_exists {
  my $struct = shift;
  while (@_) {
    my $key = shift(@_);
    return false unless exists $hash->{$key};
    $hash = $hash->{$key};
  }
  1;
}

my $x = {};
if (my_exists($x, 'a', 'c')) {
  print "c exists\n";
} else {
  print "c doesn't exist\n";
}
print Dumper($x);
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