my %phrases = (
 "phrase 1" => {
   qty        => 1,
   qtySum     => 5,
   qtyCont    => 8,
 },
 "phrase 2" => {
   qty        =>10,
   qtyCont    =>34,
 },
 "phrase 3" => {
   qty        =>1,
 },
);

for my $k (keys %phrases) {
 # update
 # $phrases{$_}->{ qtyTotal} = sub { qtyTotal($_) }
 $phrases{$k}->{ qtyTotal} = sub { qtyTotal($k) }
}

sub qtyTotal{
 my $qty = 0;
 my $key = shift;
 my $phObj = $phrases{$key};
 foreach my $qType ('qty', 'qtySum', 'qtyCont'){
  $qty += $phObj->{$qType} if exists $phObj->{$qType};
 }
 return $qty;
}