I went to the CPAN site but couldn't retrieve much about this module

I'm not sure what you mean. I gave you a link to the full documentation for the module. If what you want isn't there, then perhaps you should report a documentation bug :-)

If I comment out this line "use Mozilla::LDAP::API qw(:constant :api :ssl);" then the error that it gives is : Undefined subroutine &main::ldap_init

That's not really a surprise when you think about it. If you comment out the module which supplies a subroutine then Perl won't be able to find the subroutine.

If you find that confusing then I recommend that you step back from this project and try reading some good books.

You haven't taken the effort to format your code in a readable manner - therefore I'm not going to make the effort to read it.

Also, you've completely ignored the requests to tell us what messages are being written to the web server error log. If you want our help, then you should answer the questions that we ask.