Your desired changes are trivial then.

I did the demo in the debugger to help you experiment. Please use strict and warnings when translating into a script.

We are glad to answer your questions.

°) could also be translated into a 3 level for loop if it's easier to understand for you.

Thanks LanX.

I'm trying to modify your code to handle update #2 in my original post, i.e. this line:

@hash{@keys} = ('value2') x @keys
[download]

This test seems to work as I want it to:

perl -MData::Dump -e '@hash{(key1,key2)} = ({a=>1, b=>2},{a=>1,b=>2});
+dd \%hash'
{ key1 => { a => 1, b => 2 }, key2 => { a => 1, b => 2 } }
[download]

But when I try to multiply the values out, it doesn't:

perl -MData::Dump -e '@hash{(key1,key2)} = ({a=>1, b=>2}) x 2;dd \%has
+h'
do {
  my $a = { key1 => { a => 1, b => 2 }, key2 => 'fix' };
  $a->{key2} = $a->{key1};
  $a;
}
[download]

And the debugger didn't shed any light for me, either.
What am I doing wrong, please?  And what's that 'fix' thing about?