my %seen;
while (<>) {
   if (s/\\\n\z/ /) {
      my $next = <>;
      if (defined($next)) {
         if ($next =~ /^\s*-end\s/) {
            $_ .= $next;
         } elsif ($next =~ /(\\\n)\z/) {
            $_ .= "\\\n";
         } else {
            $_ .= "\n";
         }
         redo;
      }
   }

   print if /^data\s/ && !$seen{$_}++;
}