my %myHash = (
  "FredFlintstone" => 1000,
  "BarneyRubble" => 2000,
);

foreach (keys %myHash) {
  $var = "money_spent_$_";
  $$var = $myHash{$_};
}

say $money_spent_FredFlintstone; # 1000
say $money_spent_BarneyRubble;   # 2000