sub prospects {
  $b->{SALARY} <=> $a->{SALARY}
    ||
  $b->{HEIGHT} <=> $a->{HEIGHT}
    ||
  $b->{AGE} <=> $a->{AGE}
}

@sorted = sort prospects @recs
##</code><code>##

[
 { 
   KeyName => 'SALARY',
   SortType => '<=>' 
 },
 { 
   KeyName => 'FIRST_NAME',
   SortType => 'cmp'
 }
]