my @today = (localtime)[3..5]; # gets day, month-1, and year
my $last_modified = (stat($tied_hash_file))[9]; # grab the modification time
my @last_modified_date = (localtime($last_modified))[3..5];

# search perlfaq4 (I think) for the compare_array routine!

# ... tie the hash, then

%tied_hash = () unless compare_array(\@today, \@last_modified_date);