#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;

my %records = ();
my $ref = \%records;

print "Before call to DoStuff\n";
print "Hash reference: '$ref'\n";
print Dumper(\%records);
DoStuff(\%records);
print "Back from call to DoStuff\n";
print Dumper(\%records);
exit(0);

sub DoStuff
{
  my $hash_ref = shift;
  print("In DoStuff: ");
  print "Hash reference: '$hash_ref'\n";
  my %temp_records = %{ $hash_ref };
  $temp_records{"foo"} = "bar";
  print Dumper(\%temp_records);
  return;
}

##</code><code>##

Before call to DoStuff

Hash reference: 'HASH(0x1da6e78)'

$VAR1 = {};

In DoStuff:
Hash reference: 'HASH(0x1da6e78)'

$VAR1 = {
          'foo' => 'bar'
        };

Back from call to DoStuff

$VAR1 = {};