sub new {
	...
        my %self = %{$_[0]} if ref $_[0];
	...
}

##</code><code>##

use strict;
use warnings;
my $a = testref1();
my $b = testref1();
$b->{test}="";
$a->{test}="hello world";
print $b->{test} . "\n\n";

my $c = testref2();
my $d = testref2();
$d->{test}="";
$c->{test}="hello world";
print $d->{test} . "\n\n";

sub testref1{
        my %x = %{$_[0]} if ref $_[0];
        print "testref1:" . \%x . "\n";
        return(\%x);
}

sub testref2{
        my %x;
        %x = %{$_[0]} if ref $_[0];
        print "testref2:" . \%x . "\n";
        return(\%x);
}

##</code><code>##

testref1:HASH(0x9f952c4)
testref1:HASH(0x9f952c4)
hello world

testref2:HASH(0x9f95864)
testref2:HASH(0x9f7b7a4)