my $seen_16r_secmove = 0;
my $seen_17b         = 0;
my @buf;
while (<>) {
   if (/^:17B:/) {
      $seen_17b = 1;
      print @buf;
      @buf = $_;
      next;
   }

   $active = 1 if /^:16R:SECMOVE$/;

   if (!$seen_17b || $seen_16r_secmove && /^:35B:/) {
      print;
   } else {
      push @buf, $_;
   }
}

print @buf;