sol1.pl

use strict;
use warnings;
use v5.14;
use List::Util qw/sum/;
use Data::Dumper;

sub diff_sum {
  my ( $l_ref, $g_ref ) = @_;
  return sum(@$l_ref) - sum(@$g_ref);
}

sub add_to_hash {
  my ( $h_ref, $key, $value ) = @_;
  $h_ref->{$key} = $value;
}

say diff_sum([2, 3, 5], [2, 4, 5]);

my %h = ( a => 1, b => 2 );

print Dumper( \%h );
add_to_hash( \%h, c => 3 );
print Dumper( \%h );