use strict;
use warnings;

use Data::Rmap qw(:all);
use Data::Dumper;

my $initial_lol = [ note => [ shopping => [ item => 'sample' ] ] ];

#  In $initial_lol, the new child of shopping is shopping_items
my $new_lol = newnode($initial_lol, item => shopping_items());

warn Dumper($new_lol);



sub newnode {
  my ($lol, $node_label, $new_node)=@_;

  my ($mapresult) = rmap_array {
 

  if ($_->[0] eq $node_label) {
    $_ = shopping_items();
    cut($_);
  } else {
    $_;
  }

  } $lol;

  $mapresult;

}

sub shopping_items {
  my @shopping_items;
  for my $item qw(bread butter beans) {
    push @shopping_items, [ item => $item ];
  }
  \@shopping_items;
}