I think you've grasped the problem by mentioning eval. $new_hash{ '{key1}{key2}{key3}' } is the actual key you're accessing, which is a Bad Thing™.

You could use eval, but that would be wasteful:

$\ = "\n";
foreach (eval "keys \%{ \$new_hash->$key }" ){ print }
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I think it's worth mentioning that %$new_hash and %hash1 are two names for the same thing.

That set aside, here's a solution matching you're concept:

my @path = qw(key1 key2 key3);

my $reference = $new_hash;

$reference = $reference->{$_} foreach @path;

$\ = "\n";
foreach (keys %$reference){
    print;
}
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Update: I suggest rereading perlreftut and perlref to farmiliarise yourself with the concept of pointing at a structure. Perhaps you'll find a more suitable solution.

-nuffin
zz zZ Z Z #!perl