in reply to sort HoH by second level values in specific order

See also List::UtilsBy on how to specify the sort routines in a simpler way (without using $a and $b, that is). Unfortunately, you can't easily translate nested sorts to it (or sort1($a, $b) || sort2($a, $b): you need to create a single key for each element and compare it as a string or as a number. 
use List::UtilsBy qw{ sort_by };

say join "\t", @{ $free_space->{$_} }{qw{ cores mem }}, $_
    for sort_by {
          sprintf('%03d', 1e4 - $free_space->{$_}{cores})
        . sprintf('%05d', 1e6 - $free_space->{$_}{mem})
        . $_
    } keys %$free_space;

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($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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