#!/usr/bin/perl

use strict;
use Data::Dumper;

my %input = {foo => 'bar', oof => 'wha'};
my_sub(\%input);

$input{foo} = 'bar1';
my_sub(\%input);

sub my_sub {
    my $ref = shift;

    my %args = (
        foo => 'oop',
        pah => 'meh',
        oof => 'off',
        %{$ref}
    );

    warn Dumper(\%args);
}