disconnected copy of hash array

When I create a copy of a hash array, the operation on the copy hash 
seems to affect the original hash
( when the values are reference elements ) 

How do I avoid this ?

In the following script %y is a copy hash , but change that and the %x 
original hash is affected

--------------
#!/usr/bin/perl
use strict;
use warnings;

my %x = ( a => [1]);
foreach my $i( 1 .. 5){
  my %y = %x;
  push @{$y{a}},5;
  print "[Loop $i] " . join(" ",@{$x{a}}) ."\n";             # I want 
this to be same in every loop 
}
----------------

Output 
---------
[Loop 1] 1 5
[Loop 2] 1 5 5
[Loop 3] 1 5 5 5
[Loop 4] 1 5 5 5 5
[Loop 5] 1 5 5 5 5 5
-------------

But I dont want the original %x to get affected. How do I do this ? 

Thanks
Ram

[Apologies , if you see this message twice. Last time my browser crashed ]