If I use print CGI::Dump(), it also show me:
# chk_idx
* 2001
* 2002
...
* 2762
# ch
but I have no ch variable defined, and in Dump() list, variable ch has no value. I think, this can be same problem connected with max POST_PARAM_SIZE in somewhere in CGI, because if I use Webmin::ReadParse, it parses input params correctly.