sort upper case just before lowercase key values from a hash

Question

I have an hash and i want to sort based on the keys with upper case words appearing just before the lowercase words.

Example:

JANE
jane
JIM

Answer 1

To get the keys in order, apply sort with a custom sort function on the keys of the hash.

my %hash = ( JANE => 1, jane => 2, JIM => 3, jim => 4 );
my @sorted_keys = sort {
    lc $a cmp lc $b
        || $a cmp $b
} keys %hash;

This custom sort function compares strings first as if they were of the same case, and if equal, takes case into account.