You could avoid repeated double-lookups with a Schwartzian sort:

my @sorted_keys = map {$_->[0]}
    sort {$a->[1] cmp $b->[1]}
    map {[$_, $hash{$_}{this}]} keys %hash;
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(Read it bottom to top and it will make more sense.)

This is more memory intensive, but doing the double lookup in the sort block means that it happens O(n * log(n)) times. Doing it in a map means it only happens n times. (Where n is the number of keys.)