sub             sub
        {
\               my $file = shift;
\
\               $file =~ m#(.+)/([^/]+)\.zone$# or die "parse error";
\               my $admin_dir = $1;
\               my $domain_name = $2;
\
\               my @mx;
\               my $stuff = "\$INCLUDE $file\n";
\               my $origin = $domain_name;
\               my $this_name;
\               while ( 1 )
\               {
\                       last if ( $stuff =~ m/^\s+$/ );
\
\                       $stuff =~ s/^\s*\n// and next;
\                       $stuff =~ s/^\s*;.*\n// and next;
\
\                       if ( $stuff =~ s/^\$ORIGIN\s+(\S+).+?$//i )
\                       {
\                               $origin = $1;
\                               next;
\                       } 
\
\                       if ( $stuff =~ s/^\$INCLUDE\s+(\S+).*?$//i )
\                       {
\                               local $/;
\                               my $fh = new IO::File "< $1" or die "could not open $1";
\                               $fh->input_record_separator(undef);
\                               $stuff = <$fh> . $stuff;
\                               close $fh;
\                               next;
\                       }
\
\                       $stuff =~
\                       s/
\                               ^
\                               \s*
\                               (?:(\S+)\s+)?
\                               (?:\d+\s+)?
\                               (?:IN\s+)?
\                               (?:([a-zA-Z]+)\s+)
\                               (
\                               (?:
\                                       [^\(\n]+ (?: \; .* )?
\                                       |
\                                       \(
\                                       (?:
\                                               [^\)\n\;]*
\                                               (?: \; .* )? \n
\                                               |
\                                               [^\)\n\;]+
\                                       )*?
\                                       \)
\                               )+?
\                               )
\                               \n
\                       //x
\                       or ( $stuff =~ s/^.*\n//, next );
\                       my ($name, $rtype, $rinfo) = ($1, $2, $3);
\                       $this_name = $name if ( defined $name );
\                       $this_name = $origin if ( $this_name eq "@" );
\
\                       if ( lc($rtype) eq "mx" and $rinfo !~ /;\s*<?norcpthosts?>?/i )
\                       {
\                               my $fh = new IO::File "< $admin_dir/info.username"
\                                       or die "no info.username file\n";
\                               my $username = <$fh>;
\                               chomp $username;
\                               undef $fh;
\                               push @mx, "$this_name:$username";
\                       }
\               }
\
\               return [join("\n", @mx), [] ];
        }
-----

One condition for use: if you do use this code to create
a zone file syntax checker, please tell me about it.
  ~ David Harris <dharris@drh.net>