The Net::DNS::Zone::Parser should be considered a preprocessor that "normalizes"
a zonefile.

It will read a zonefile in a format conforming to the relevant RFCs with the
addition of BIND's GENERATE directive from disk and will write fully specified
resource records (RRs) to a filehandle. Whereby:
- All comments are stripped
- There is one RR per line
- Each RR is fully expanded i.e. all domain names are fully qualified
  (canonicalised) and the CLASS and TTLs are specified.
- Some RRs may be 'stripped' from the source or otherwise processed. For details
  see the 'read' method.

Note that this module does not have a notion of what constitutes a valid zone,
it only parses. For example, the parser will happilly parse RRs with ownernames
that are below in another zone because a NS RR elsewhere in the zone.