#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my ($user,$password);

my $a=0;
my %hash1 = map{$a++=>$_}qw/\$user \$password/; #just text
my %hash2 = map{$a++=>$_}(\$user, \$password);  #real reference

print Dumper \%hash1, \%hash2;

$user     = 234;
$password = 'xyz';

print Dumper \%hash1, \%hash2;
__END__
$VAR1 = {
          '1' => '\\$password',
          '0' => '\\$user'
        };
$VAR2 = {
          '3' => \undef,  #ref to an undefined val
          '2' => \undef
        };
#################
$VAR1 = {
          '1' => '\\$password',
          '0' => '\\$user'
        };
$VAR2 = {
          '3' => \'xyz', #see changing $user or $password
          '2' => \234    #did update the hash
                         #because these are real references.
        };