I wouldn't delete during the traversal. I'd save all the names and delete afterwards:

use File::Find qw(find);
use File::Path qw(rmtree);

@ARGV = qw(.) unless @ARGV;

my @goners;
find sub {
  return unless -d;
  return unless $_ eq "_vti_cnf";
  $File::Find::prune = 1; # don't descend, gone later anyway
  push @goners, $File::Find::name;
}, @ARGV;

rmtree \@goners, 1, 1; # trace, and ignore undeleteables
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