#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11131585
use warnings;

my $orig = { a => { b => ["c", "d"], e => [["f"]] } };
use Data::Dump 'dd'; dd 'orig', $orig;

my $augment = { a => { b => [ 'c', 'd' ], e => [ [ 'g' ] ] } };
use Data::Dump 'dd'; dd 'augment', $augment;

my $delta = reduce( $orig, $augment );
use Data::Dump 'dd'; dd 'delta', $delta;

sub reduce
  {
  my %augment = map { $_ => '' } buildstatements( pop );
  delete @augment{ buildstatements( shift ) };
  eval join '', %augment for my $delta; # HAHAHAHAHAHA
  return $delta;
  }

my @buildcode;
sub buildstatements
  {
  @buildcode = ();
  creators( '$_->', shift() );
  return @buildcode;
  }

sub creators
  {
  my ($have, $ref) = @_;
  if( 'HASH' eq ref $ref )
    {
    creators( $have . "{$_}", $ref->{$_} ) for keys %$ref;
    }
  elsif( 'ARRAY' eq ref $ref )
    {
    creators( $have . "[$_]", $ref->[$_] ) for 0 .. $#$ref;
    }
  else { push @buildcode, qq($have = "$ref";); }
  }