I answered this in the CB when you asked there. Here it is again since you asked again.

• You're assigning a list of keys to a hash when it takes a list of key-value pairs.

• You assume the order of the key-value pairs you assign to a hash matters, but it doesn't.

• As for the waning, it says you shouldn't use split to assign to @_. That's particularly true here since you don't want to assign to @_. (See the docs.) You can use $s=~tr/d// to count the number of instances of "d". You could also use (()=$s=~/d/g).

my @sorted_keys = sort { $a=~tr/d// <=> $b=~tr/d// } keys(%hash);
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