package Dictionary;
...
sub check {
   my $self = shift;
   my $error;
   foreach (@{$self->{children}}) {
      $error++, last unless $_->check(@_)
   }
   return !$error;
}

package Entry;
...
sub check {
   my $self = shift;
   return 1 if $self->{value} > 0;  # or whatever
   return;
}