In my experience, there are two ways of using hashes. One is as a lazy-programmer's object. You see these kinds of hashes returned from database queries, received from REST API requests, etc. Something like this:

my $uncle = {
  name => 'Bob',
  age  => 45,
};
[download]

In these cases, the keys are an already-known set of strings, usually picked to be identifier-like (no spaces, weird punctuation, etc), so I will usually not quote keys in this kind of hash.

The other way of using hashes is as basically a mapping from values of one type to values of another type. For example:

my %ages = (
  'Alice'    => 41,
  'Bob'      => 45,
  'Carol'    => 38,
);
[download]

Quoting the keys for this kind of hash is useful because you never know when another value is going to be added which isn't a safe identifier ($ages{"d'Artagnan"} = 62) plus it helps visually distinguish the second kind of hash from the first kind of hash.

Do I consistently follow this rule? Absolutely not.