And further to your reply ... ;-)

plain printing of the references reveals that the last are identical objects

  DB<61>  @ra = ({a=>1, b=>2}, {a=>1, b=>2});

  DB<62> print $_ for @ra
HASH(0x35a4090)HASH(0x35a3ae8)           # different IDs
  DB<63>  @ra = ({a=>1, b=>2}) x 2;

  DB<64> print $_ for @ra
HASH(0x35a3eb0)HASH(0x35a3eb0)           # same IDs
  DB<65>
[download]

> Update: dd works by generating source code that will reproduce the structure of the data being dumped.

... when run thru eval .

There seems to be no better generic syntax to reproduce the case of duplicated references, than stuffing a fix placeholder string into it and fixing it later.

An for completeness, here code to clone the hashes instead of copying their refs

my $value = { a=>1, b=>2 };    # curly brackets to assign hashref!
$hash{$_} = { %$value } for @keys;

### or alternatively

my %value = ( a=>1, b=>2 );    # round brackets to assign list!
$hash{$_} = { %value } for @keys;
[download]

this kind of cloning works because % returns a list in listcontext, which is packed again into a new { hash }

  DB<78> x %$value
0  'a'
1  1
2  'b'
3  2
  DB<79>
[download]

debugger demo

  DB<72> x @keys
0  'Prefix1=A:b:1'
1  'Prefix1=A:b:2'
2  'Prefix1=A:c:1'
3  'Prefix1=A:c:2'
  DB<73> x $value = {a=>1, b=>2};
0  HASH(0x35a48e8)
   'a' => 1
   'b' => 2
  DB<74> $hash{$_} = { %$value } for @keys;

  DB<75> x \%hash
0  HASH(0x3598330)
   'Prefix1=A:b:1' => HASH(0x35a50b8)
      'a' => 1
      'b' => 2
   'Prefix1=A:b:2' => HASH(0x35a4c18)   # <--- differing IDs
      'a' => 1
      'b' => 2
   'Prefix1=A:c:1' => HASH(0x35a46a8)
      'a' => 1
      'b' => 2
   'Prefix1=A:c:2' => HASH(0x35a4a50)
      'a' => 1
      'b' => 2
  DB<77>
[download]