my %HoH = (
 yadda1 => {
    key1 => "value1",
    key2 => &GetValue, # returns date string
    key3 => &Compare($var1,$HoH{yadda1}{key2}),
 },
 yadda2 => {
    key1 => "value1",
    key2 => &GetValue, # returns date string
    key3 => &Compare($var1,$HoH{yadda2}{key2}),
 },
);