$ demo() {
   perl -e'
      use v5.18;
      use Hash::Ordered qw( );
      my $h = Hash::Ordered->new();
      $h->set( $_, 1 ) for "a".."z";
      say $h->keys;
   '
}

$ demo
abcdefghijklmnopqrstuvwxyz

$ demo
abcdefghijklmnopqrstuvwxyz