use strict;
use warnings;
use Data::Dump qw();
use Data::Rmap qw();

my $initial = [note => [shopping => ['item']]];

Data::Rmap::rmap_array {
    return $_ if $_->[0] ne 'shopping'; # Ignore non-shopping entries

    my @item= map {[item => $_]} qw(bread butter beans);

    $_->[1] = ['shopping', @item];
    Data::Rmap::cut ($_);
} $initial;

print Data::Dump::dump ($initial), "\n";