#!/usr/bin/perl --
use strict;
use warnings;
use Data::Dump qw/ dd /;
use Template::Stash;
use Template::Stash::XS;
for my $stash ( Template::Stash::XS->new, Template::Stash->new ){
    $stash->set('group', [ 'one' ]);
    $stash->set('g', $stash->get(['group', 0, 1, 0]));
    dd( $stash->get('g' ) );
    $stash->set('g', $stash->get(['group', 0, 1, 0, 'defined', 0]));
    dd( $stash->get('g' ) );
    $stash->set('g', $stash->get(['g', 0, 'defined', 0]));
    dd( $stash->get('g' ) );
    dd( $stash->set('undy', undef ) );
    dd( $stash->get('undy' ) );
    dd( $stash );
}
__END__
$ perl template-stash-bug.pl
""
""
1
""
""
bless({
  _PARENT => undef,
  dec => sub { ... },
  g => 1,
  global => {},
  group => ["one"],
  inc => sub { ... },
  undy => undef,
}, "Template::Stash::XS")
""
""
1
""
""
bless({
  _PARENT => undef,
  dec => sub { ... },
  g => 1,
  global => {},
  group => ["one"],
  inc => sub { ... },
  undy => undef,
}, "Template::Stash")